Introduction

Maternal metabolism changes significantly in pregnancy [1–16]. The first stage of gestation is characterised by an anabolic state with an increase in maternal fat stores and a modest increase in insulin sensitivity to meet maternal and foetal demands for nutrients throughout pregnancy and lactation (facilitated anabolism) [1]. The later stages of pregnancy coincide with a catabolic state and lower insulin sensitivity (higher insulin resistance) triggered by placen-tal hormones [1–10]. This increases the concentrations of glucose and free fatty acids, ensuring a further increase in the nutrients available to the foetus. In normal pregnancy, this results in an increased beta cell mass (due to beta-cell hypertrophy and hyperplasia), which, along with an increase in insulin secretion, compensates for the insulin resistance characteristic of gestation [2, 4, 8].

Gestational diabetes mellitus (GDM) develops if beta-cell secretion is insufficient to compensate for peripheral insulin resistance [4, 8]. Recent studies have shown the important role played by microRNA [17], oxidative stress and inflam-mation, and lipotoxicity in determining insulin resistance [8, 9, 18, 19]. These alterations together with changes in triglyceride and protein levels contribute to abnormal foetal growth, such as macrosomia [13, 20–22].

    In pregnancy complicated by pregestational diabetes, maternal hyperglycaemia is known to raise the risk of foetal and newborn morbidity due to maternal-to-foetal hyperinsu-linemia [23, 24]. The transplacental flux of glucose causes foetal hyperglycaemia and hyperinsulinemia, resulting in accelerated foetal growth and macrosomia [13, 20, 22]. However, some clinical studies have shown there is still a high frequency of macrosomia in diabetic pregnant women, even when they have normal glycaemic values [27]. Fol-lowing from this, the “Foetal Glucose Steal” hypothesis was formulated: the normal foetal pancreas secretes insulin rather slowly, but exposure to hyperglycaemia can upregu-late foetal insulin secretion. Early onset of foetal hyperinsu-linemia can lower foetal glycaemia, thereby increasing the glucose concentration gradient across the placenta, which increases glucose transfer to the foetus triggering growth and an increase in foetal fat [27].

    Obesity per se is characterised by insulin resistance, which is amplified in pregnancy activating oxidative stress, inflammation and modification of triglyceride levels, which can impair foetal growth [25–28]. Furthermore, pre-preg-nancy maternal BMI and the size of the placenta are cor-related with the weight of the child in obese women [29].

    So, after 44 years the Freinkel hypothesis on foetal growth is still supported [26, 27].

    The recommendations presented here, which are based on national and international guidelines and the most recently published data on nutrition in physiological preg-nancy and pregnancy complicated by hyperglycaemia and/ or obesity, are designed to help healthcare professionals pre-scribe suitable eating patterns to safeguard the health of the mother and the foetus. This systematic review is an update of a previous version about the MNT for pregnant women performed in 2014 (Alimentazione in Gravidanza: racco-mandazioni SID AMD ADI).

BOX 1

Physiological pregnancy is characterised by: – Accelerated fasting. – Facilitated anabolism.

Diabetic pregnancy is characterised by: – High/increased insulin resistance. – Relative deficit in the 1st phase of insulin secretion. – Failure to adapt insulin secretion to the increased

Pregnancy in obese women is characterised by: – High pre-pregnancy insulin resistance. – chronic inflammation.

Methods

    This systematic review used a comprehensive search strat-egy using key words related to pregnancy, medical nutrition therapy, clinical practice guidelines, pregnancy complicated by gestational diabetes, pregnancy complicated by pregesta-tional diabetes, pregnancy complicated by obesiy.

    Full guidelines, international recognized committee, cochrane review, Randomized Clinical Trials (RCT) avail-able in MEDLINE, EMBASE, PubMed, Scopus in Eng-lish up to November 30th 2024 were utilized. Furthermore Italian Guidelines and reccommendations were taken into consideration.The level of scientific evidence underlying each recommendation has been classified according to the National Guideline Plan (www.pnlg.it), (supplementary Tables s1,2). 

Energy demands and nutritional requirements in pregnancy

Energy intake and weight gain

    Correct nutrition is an indispensable requirement for a suc-cessful pregnancy. An adequate increase in body weight and a good nutritional status are necessary to meet maternal energy demands and provide the foetus with the nutrients needed for its development [30–32]. During pregnancy, pro-found metabolic changes linked to hormonal variations are partly responsible for ever-increasing energy needs. In the second half of gestation, rapid foetal growth and increased cardiovascular and respiratory rates raise the basal metabo lism by 60%, but by about 30% in overweight women [33, 34]. The increase in maternal fat mass is the most vari-able component of weight gain, contributing to the energy costs of pregnancy and correlating positively with weight gain [32], especially in obese women [35, 36]. Although there is an estimated total additional energy requirement of ⁓76,000 kcal during the entire pregnancy (associated with a maternal weight gain of approximately 12 kg), there is inter-individual variation in energy expenditure, linked not only to weight gain but also to nutritional status [37]. The mag-nitude and composition of appropriate weight gain differ significantly between women depending on their pre-preg-nancy BMI [38] (Table 1). In general, in the first trimester, unless the woman enters pregnancy with insufficient energy reserves (as in the case of underweight women), the calorie requirement does not need to be increased. From the second

trimester onwards, however, the increase in maternal tissues and foetal growth require a gradual increase in calories [38]. In particular, LARN (2024) [37] recommends an additional 350 kcal/day for a pregnant woman of normal weight in the second trimester and 460 kcal/day in the third trimester. There will be a smaller increase where physical activity is reduced [Level of evidence III, Strength of recommenda-tion A].

    These principles determine a calorie requirement of 1800–2400 kcal/day. Correct energy intake should result in an overall weight gain in line with Institute of Medicine (IOM) recommendations for the different BMI classes [38] based on a systematic review of the literature (Table 1) and accepted by Italian national bodies [39] [Level of evidence III, Strength of recommendation B].

    No studies have been conducted on the energy needs and required weight gains in twin pregnancies. Instead, theoreti-cal evaluations have been carried out from data from single pregnancies, based on which some authors have hypothe-sised an increase in energy requirements for the 2nd twin of around 150 kcal/day. The Canadian Higgins Nutrition Inter-vention Program, however, recommends an increase of 1000 Kcal per day (500 for each twin) from 20 days [40]. Based on a few studies performed on a single cohort of women, the IOM [38] recommends the following weight increases in twin pregnancies (two foetuses): 16.8 to 24.5 kg for women of normal weight, 14.1 to 22.7 kg for overweight women, and 11.4 to 19.1 kg for obese women. [Level of evidence IV, Strength of recommendation C]. A 2019 study vali-dated the IOM recommendations retrospectively through analysis of 878 twin pregnancies: the results showed, in particular, that a greater weight gain increased the risk of pre-eclampsia and gestational hypertension, a lower weight gain increased the risk of preterm birth, low birth weight, respiratory distress and hospitalisation in a neonatal inten-sive care unit (NICU) [41]. A recent meta-analysis of the appropriateness of the IOM recommendations for different ethnicities (American, European and East Asian) found no risk of small for gestational age (SGA), large for gestational age (LGA), macrosomia or caesarean section in women of different ethnic groups with weight gains above or below the recommendations if specific BMI classes are taken into account for Asian women [42].

    In this frame it is important to take into considerations that BMI class are different only for Asian people in which normal weight is defined as a BMI≤22,9 kg/m2 ,overweight between 23 and 26.9 and obesity≥27 kg/m2 [38].

Weight gain in pregnant women with diabetes

    So far, no specific weight goals have been defined for preg-nant women with diabetes other than those relating to pre-pregnancy BMI [38]. Recent studies suggest that stricter

weight control for women with GDM where it is associated with obesity could reduce the incidence of negative neona-tal outcomes, such as macrosomia and LGA births [43]. A recent population-based cohort study of 1,338,460 women with GDM in the USA showed that weight gain was asso-ciated with composite outcomes, including preterm birth, LGA and SGA. The study also showed that the severity of the composite outcome had a U-shaped or J-shaped rela-tionship with weight gain across the BMI categories. Ges-tational weight gain above the targets defined both by the authors and by the IOM was associated with an increase in adverse perinatal outcomes. Interestingly, weight gains below the IOM targets and the study targets reduced to a similar extent the incidences of adverse perinatal outcomes in women with GDM, with the exception of those with class 2 and class 3 obesity. The authors concluded from their results that the optimal gestational weight gains for women with moderate or severe obesity may be lower than the IOM guidelines (respectively, -2.4 to -8.2 kg and −8.3 to -6.0 kg) [44]. However, other studies found that stricter weight tar-gets did not improve perinatal outcomes in women with GDM [45]. Nonetheless, it should be borne in mind that other factors may also play a role, such as maternal glycae-mic control, pre-pregnancy BMI and maternal hypertriglyc-eridemia [46].

Weight gain in obese pregnant women

    The correct gestational weight gain for women with pre-pregnancy BMI≥30 kg/m2 is still a controversial issue. Most et al. built a linear model to predict changes in body compo sition (fat mass, lean mass) in women with class 2 and class 3 obesity and with appropriate weight gain. Assuming an increase in free fat mass (FFM) comparable to other classes of BMI and the inverse association between pre-pregnancy BMI and fat mass gain across all BMI classes, their model predicted how maternal fat mass should be lost during preg-nancy in cases of morbid obesity (BMI≥40 kg/m2 ) in order to optimise pregnancy outcomes [47]. Studies on energy expenditure have shown that the recommended weight gain in pregnancies complicated by obesity is reached when the daily energy intake does not exceed total energy expendi-ture [48]. In fact, the energy requirements of obese women for foetal development should be offset by the mobilisation of maternal fat mass without negative effects on maternal and foetal outcomes. The authors proposed a daily reduc-tion of approximately 100 kcal to ensure the recommended weight gain [48]. The increase in energy needs in the sec-ond and third trimesters recommended by both international and Italian guidelines [37, 38, 49] should not, therefore, be applied universally to all BMI classes. Recent studies [50–52] have shown that little or no increase in weight or a modest weight loss can reduce the risk of LGA without a significant increase in SGA, suggesting that the weight gains recommended by the IOM should be re-evaluated for obese women and should be defined according to obesity class. There is also a need for further studies to assess the role of dietary patterns and quality. However, it is worth remembering that no data on calorie restriction in physi-ological pregnancy are currently available, and therefore extremely low-calorie diets are not recommended in cases of severe obesity.

Macronutrients (Table 2)

During pregnancy the protein requirement significantly increases, while carbohydrate and fat requirements remain almost unchanged (37) [Level of evidence I, Strength of recommendation A].

Proteins

Protein should provide about 20% of daily energy. The majority of this intake should come from organic plant-based foods containing high-value proteins or from proteins of animal origin, such as milk, meat and eggs. During preg-nancy, protein intake needs to be progressively increased, especially in the 3rd trimester (+1 g/day in the 1st trimester, +9 g/day in the 2nd, +29 g/day in the 3rd) (37). [Level of evidence I, Strength of recommendation A].

Carbohydrates

The main sources of energy even during pregnancy are car-bohydrates (CHO), supplied mainly by polysaccharides, and must account for 45–60% of total daily energy. Daily intake should not be less than 175 g to adequately meet the needs of both the maternal and foetal brain [53]. When choosing foods, preference should be given to wholegrain cereals to ensure an adequate fibre intake. The consumption of sug-ary drinks and sweets should be limited [Level of evidence I, Strength of recommendation A]. A recent study showed that the placenta also consumes glucose, at approximately 36 g per day, so the glucose intake during pregnancy should be 220 g/day, rather than the 175 g/day currently recom-mended. However, further studies are necessary to confirm this finding [54].

Fats

Fat-derived energy should be between 20 and 35% of total daily energy. Saturated fats must not exceed 10% of total energy (with a cholesterol intake of less than 300 mg/day). Since it is important to maintain an adequate intake of essential fatty acids during pregnancy, the remaining por-tion of lipids should be composed of the polyunsaturated fatty acids omega-3 and omega-6, and monounsaturated fatty acids. DHA (docosahexaenoic acid, an omega-3) is of particular importance due to its role in the development of the retina and nervous system of the foetus [55]. There is no population recommended intake (PRI) in pregnancy, although the new LARN suggests a reference amount of 100–200 mg/day [37] [Level of evidence I, Strength of rec-ommendation A].

Vitamins (Table 2)

If the woman’s diet is varied and she consumes foods such as fruit, vegetables and milk, all vitamin requirements are guar-anteed and no particular supplementation is recommended, with the exception of folic acid. An increased intake of folic acid during pregnancy of at least 400 micrograms/day has proven effective in preventing spina bifida and anenceph-aly [55, 56]; a supplement of 5 mg/day is recommended for women who have delivered foetuses with neural tube defects, are genetically predisposed to neurological patholo-gies/malformations, or have pre-gestational diabetes or obe-sity [57] [Level of evidence I, Strength of recommendation A]. Folic acid supplementation should be started one month before conception and continued during pregnancy up to the 12th week of gestation [57]; women at high risk of adverse maternal and foetal outcomes are advised to begin supple-mentation of 5 mg/day 3 months before conception [57]. The risk of toxicity from supplements and/or foods fortified with folic acid is low [57] as it is a water-soluble vitamin and the excess is eliminated via urine. LARN guidelines set the maximum tolerable limit in pregnancy at 1000 µg/day; neurotoxicity is documented for intakes>5000 µg/day [37].

There is no agreement regarding optimal vitamin D plasma levels during pregnancy [37, 38, 57–59]. LARN [37] states that Vitamin D requirements do not change with pregnancy but remain at 15 µg/day (i.e. 600 IU/day). Vita-min D supplementation is therefore not necessary for any women and is only recommended for those at risk of hypo-vitaminosis (women of Southeast Asian, African, Caribbean and Middle Eastern origin, women on diets low in vitamin D) [58, 59] [Level of evidence III, Strength of recommen-dation B]. NICE recommends all women take a vitamin D supplement of 10 µg/day during pregnancy and breastfeed-ing [57] [Level of evidence III, Strength of recommendation B]. Vitamin A supplementation has demonstrated benefits only in deprived populations (Africa, Southeast Asia) [60]. As dosages higher than the recommended levels for preg-nant women (700 µg RE) are associated with an increased risk of congenital malformations [60], supplementation dur-ing pregnancy is not recommended [Level of evidence III, Strength of recommendation B].

Trace elements (minerals) (Table 2)

A diet including foods from all the food groups will cover mineral nutritional needs during pregnancy. The only excep-tions are calcium, iron and iodine. According to the new LARN [37], the calcium requirement remains unchanged from the pre-pregnancy period provided food intake is adequate. However, it is quite common for diets to have an insufficient calcium content, so pregnant women should be encouraged to consume calcium-rich foods daily. Women who do not consume milk or milk derivatives are advised to consume foods fortified with calcium or to take supple-ments. Adequate calcium intake is essential to reduce the risk of pre-eclampsia, especially in women at risk of ges-tational hypertension [61] [Level of evidence I, Strength of recommendation A]. A significant increase in iron intake during pregnancy is advised, especially from the 20th week, due to increased demands for this mineral from the foetus. Iron supplemen-tation is necessary in cases of iron deficiency anaemia [37] [Level of evidence I, Strength of recommendation A]. The recommended iodine intake during pregnancy is 220–250 mcg/day [37, 62]. In Italy, the use of iodised salt is recommended (Law no. 55 of 21 March 2005): as 1 gram of this salt contains 20–30 mcg of iodine it ensures optimal intake [Level of evidence III, Strength of recommenda-tion B]. However, during pregnancy it is useful to consume foods with a high iodine content or take iodine supplements.

Fibre

The diet must include a fibre intake of approximately 30 g per day. The consumption of foods naturally rich in dietary fibre, such as whole grains, legumes, fruit and vegetables, are recommended as these increase the intake not only of fibre, but also of vitamins and trace elements.

Caffeine and alcohol

Both caffeine and alcohol cross the placenta, so in excessive doses they can be harmful to the foetus [37, 38] [Level of evidence III, Strength of recommendation B]. A caffeine dose of 300 mg/day should not be exceeded. The evidence with regard to alcohol is not conclusive, but as a precaution we recommend abstaining from alcohol during pregnancy

Advice for controlling nausea

Nausea and vomiting are frequent during pregnancy, espe-cially in the first trimester, and can interfere with the preg-nant woman’s nutritional status. To reduce nausea, eating crackers or toast before getting up in the morning, eating small meals (every 2.5 to 3 h), eliminating caffeine, reduc-ing fats, avoiding spicy foods and taking vitamin prepara-tions after meals are useful.

Diet in pre-pregnancy and gestational diabetes

The objective of Medical Nutrition Therapy (MNT) in preg-nant women with diabetes is to ensure good maternal and foetal nutrition, that provides an adequate intake of macro-and micro-nutrients, guarantees optimal glycaemic control and avoids ketonuria/ketonemia [64, 65].

    There is no consensus on what the best nutritiona approach in terms of total energy intake and macronutrient composition in the presence of GDM is [66, 67].

    Although carbohydrates (CHO) are an important source of energy, they increase post-prandial blood glucose, which means their intake must be carefully evaluated in GDM.

    A 2021 report [66] that reviewed recent studies with the aim of identifying appropriate levels of CHO in GDM found a wide variation in intake (47–70%) and that CHO with a low glycaemic index had a lower impact on blood glucose while calorie restriction had a greater impact on foetal growth. A CHO intake≤165 mg/day (lower than the IOM recommendation) seems to be associated with a micronutri-ent deficiency, but further studies are necessary to evaluate its effects on ketonemia and on triglyceride and free fatty acid levels [66]. Excessive calorie restriction during preg-nancy is not indicated, including in GDM.

    Dietary therapy for diabetic pregnant women must be planned and personalised. In this regard, the ADA, the EASD, the American Dietetic Association and groups of experts [65–69] suggest taking into consideration the patient’s cultural, ethnic and educational background, eco-nomic situation, type of work and level of physical activity, all of which can influence adherence to the diet.

    Pregnant women with pre-gestational diabetes need particular consideration as the dietary therapy must be planned and personalised before the pregnancy. In this pre-pregnancy phase, evaluation of the woman’s eating habits and calculation of her BMI will ensure the diet is the most appropriate for her needs [65, 70] [Level of evidence III, Strength of recommendation B].

Medical Nutrition Plan

It is important to explain to GDM patients the objectives of the diet, the role of carbohydrates and their importance for maintaining normoglycaemia without developing ketosis, and the parameters that will determine the possible addition of insulin therapy [Level of evidence IV, Strength of recom-mendation B].

    In pregnant women with pre-gestational diabetes, courses on counting carbohydrates or the use of exchange lists may be useful. Periodic meetings will be necessary during preg-nancy (at least 1 per trimester) to adjust caloric intake to the various stages of pregnancy [Level of evidence III, Strength of recommendation A].

    Exchange lists group foods into categories based on similar macronutrient contents, so that foods from the same group can be exchanged with each other [71].

    The glycaemic index (GI) ranks foods containing carbo-hydrates according to the rate at which they increase blood glucose levels [72–74].

    In 2019, the International Organization for Standard-ization developed and defined the reference method and published international tables showing the glycaemic indi-ces of foods [65].

    Once the glycaemic index of a food is known it is pos-sible to calculate the glycaemic load [72–74]. Together they represent not only the quality of the carbohydrates (glycae-mic index), but also the quantity (load), thus introducing the concept of the portion actually consumed. The glycaemic index and load are useful in pathologies for which it is important to control postprandial glycaemia and insulinemia, such as diabetes and obesity [74, 75], and also in diabetic pregnancies to control post-prandial glycae-mic excursions [74, 75].

    A 2016 meta-analysis by Wei et al. found that low gly-caemic index diets reduced the risk of macrosomia in the newborns of patients with GDM. Adding fibre to these diets further reduced the risk of macrosomia and the need for insulin therapy [76]. A low glycaemic index diet is therefore advised in the care of GDM women, especially where the control of post-prandial blood glucose is difficult [77].

    Carbohydrate counting is undoubtedly the best solution for optimising metabolic control in pregnant women with type 1 diabetes and its correct use must be explained during pre-pregnancy counselling [78, 79]. Attention should also be drawn to the fact that some recent studies have shown that during pregnancy the I/CHO ratio changes in relation to the gradual increase in insulin resistance and is correlated with maternal BMI and weight gain [80–82]

Carbohydrate content

The quantity and quality of carbohydrates help control post-prandial glycaemia and are essential to ensure normal foetal growth; a significant reduction in carbohydrate consump-tion could lead to the formation of ketone bodies that are harmful to the foetus. IOM and LARN recommendations must also be applied in the treatment of diabetes during pregnancy. The consumption of foods with a low glycaemic index could be useful for maintaining a correct intake of CHO in the diet while obtaining good glycaemic control, thus reducing post-prandial peaks.

    In particular, three studies conducted with women with GDM showed that a low glycaemic index diet reduced insulin requirements [82]. A systematic literature review did not show any correlation between glycaemic index and gestational week or maternal body weight [82] [Level of evidence III, Strength of recommendation B]. Some stud-ies suggest that the consumption of CHO in association with fats and proteins in the meal reduces the glycaemic impact compared with consuming the carbohydrate alone [82] [Level of evidence IV, Strength of recommendation C].

    Post-prandial glycaemic excursions can also be reduced by dividing the carbohydrate intake into 5 or 6 meals across the day: breakfast, lunch, dinner and 2 or 3 snacks.

    The recommended fibre intake is 28 g/day or 14 g/1000 kcal/day [37]. The effects of both water-soluble and non-water-soluble fibre were evaluated in pregnant women with type 1 diabetes in relation to both insulin requirements and metabolic control and revealed inverse correlations with insulin requirements and a reduction in hypoglycaemic episodes [83] [Level of evidence IV, Strength of recommendation B]. A recent Cochrane review [84] reported the results of nine studies evaluating the effects of 11 diets of different compositions in women with GDM. This meta-analysis concluded that there is no scientific evi-dence for what might be the best dietary composition to reduce the incidences of macrosomia and/or LCA because there were too few studies and the number of subjects was low. Further studies with an adequate number of cases are therefore needed to obtain reliable indications.

    In contrast, a recent meta-analysis by Yamamoto [85] of 18 randomised studies looking at different types of nutri-tional intervention, most involving a reduction in carbohy-drates and low GI foods, found that modifying the diets of women affected by GDM had favourable effects on mater-nal glycaemic outcomes (fasting, post-breakfast and post-prandial glycaemia) and on the child’s birth weight.

    Recommendations by scientific societies regarding the nutritional treatment of diabetes during pregnancy are few and varied. NICE 2008 [86] recommends foods with a low glycaemic index, whereas the IDF [87] makes no recom-mendation on the proportion of CHO in the diet, but con-siders the low glycaemic index diet to be useful. The ADA suggests that the meal plan should be based on a nutritional assessment and dietary reference intakes (DRIs). The DRI for all pregnant women includes a minimum of 175 g of carbohydrates, 71 g of protein and 28 g of fibre [65]. The Endocrine Society [88] recommends a carbohydrate intake of between 35% and 45% of total daily energy. It should be stressed that the patient undertaking this dietary regime must be carefully monitored, especially for the possible development of ketone bodies.

    There is no standard amount of CHO recommended to all pregnant women with diabetes. The CHO content can vary between 40% and 50% of the total energy based on eating habits, with a preference for foods with a low glycae-mic index. The low glycaemic index diet is essential where CHO consumption is higher [Level of evidence IV, Strength of recommendation B]. It should, however, be pointed out that a recent systematic review of the guidelines on medi-cal nutrition therapy in GDM identified a lack of rigour in developing recommendations, a lack of interdisciplinarity, poor applicability and inadequate editorial independence [89].

    The Mediterranean diet has proven to be a healthy model that protects adults from developing metabolic syndrome (MS) and could have a similar effect during pregnancy, pro tecting the foetus from MS through an epigenetic mecha-nism [90].

Medical nutritional therapy and ethnicity

Some studies have highlighted the importance of specific dietary patterns for immigrant pregnant women with ges-tational diabetes. The development of personalised dietary plans that include foods linked to the maternal ethnicity and that respect traditional eating habits have proven effective in improving diet adherence and glycaemic profiles in immi-grant women living in countries with different eating habits to their countries of origin.

    In particular, a pilot study comparing two different dietary regimes, one based on the eating habits of the host country and one on the eating habits of the country of origin, found that women on the latter regime adhered more closely to the diet and had better fasting blood sugar and glycated haemoglobin values at the end of pregnancy [​​91].

    A recent Australian study evaluating the dietary regimes of Australian and Chinese women with GDM found that the Chinese group paid little attention to traditional eating hab-its and therefore reduced their food intake with the result that they needed macro- and micro-nutrient supplementa-tion [92].

    It is therefore essential in an increasingly multi-ethnic society to develop nutritional regimes in accordance with the woman’s ethnicity in order to encourage adherence to the diet and to optimise metabolic control [Level of evi-dence III, Strength of recommendation C]

Meals and snacks

The distribution of calories across individual meals during pregnancy is similar in cases of pre-pregnancy diabetes and GDM. In particular, women are advised to divide their daily calorie intake between breakfast (10–15%), lunch (20–30%), dinner (30–40%) and three snacks (5–10%, mid-morning, mid-afternoon and before going in bed) [93]. The moder-ate caloric content of breakfast (10–15%) is justified by the need to maintain acceptable blood sugar levels despite the morning insulin resistance typical of patients with GDM, but not uncommon in pre-pregnancy diabetes, especially as gestation progresses [93]. To maintain acceptable blood glu-cose levels a savoury breakfast is often preferable. Regarding snacks, some authors recommend that a clearly obese patient with GDM being treated with diet al.one should, to avoid excessive weight growth, take three meals with a single evening snack [93]. This snack is important to avoid fasting ketosis. Three meals and three snacks are useful for nausea and vomiting, typical of the early stages of pregnancy, and for early satiety, often caused by the abdominal bulk characteristic of the third trimester. Snacks are also essential to reduce the rapid fluctuations in blood sugar that can occur during insulin therapy [Level of evidence IV, Strength of recommendation B].

Sweeteners

Sweeteners may be nutritional (polyols, fructose, agave syrup, etc.) or non-nutritive, i.e. non-caloric (aspartame, acesulfame K, saccharin, stevia, sucralose, neotame). All of these sweeteners are approved for use in the general popula-tion, including pregnant and postpartum women [94] [Level of evidence VI, Strength of recommendation B].

    In general, moderate use is recommended during preg-nancy, although the acceptable daily intake (ADI), i.e. the quantity of a substance that a person can take every day of their life without substantial risk to health, is far greater than common usage.    However, it should be remembered that polyols in high doses have a laxative effect.

Diet in obese women

Maternal obesity is associated with a greater risk of obstetric and neonatal complications [95–97], so it is important that obese women are followed by a multidisciplinary care team in which the diabetologist/endocrinologist and the gynaeco-logist are supported by a dietician to develop a dietary plan that is personalised and provides the correct weight gain during pregnancy [65, 93].

    The American Diabetes Association (ADA) recommends that obese pregnant women reduce their daily calorie intake by 30–33% compared with the pre-pregnancy period [65, 93].

Breakfast should include foods with a low glycaemic index, since insulin resistance is greater in the morning; the post-prandial glycaemic increase may be greater with foods rich in simple carbohydrates and/or with a high glycaemic

    According to recently published work, weight gains lower than those recommended for class 3 obese women or for weight loss may be acceptable during pregnancy only if individually determined to ensure an adequate carbohydrate intake to prevent ketosis and foetal growth is monitored. Moderate caloric restriction (20–25 Kcal/kg) while ensuring an adequate intake of proteins and carbohydrates for the ges-tational age may be the best strategy to manage weight gain during pregnancy. Even in obese pregnant women, caloric and carbohydrate intake must not fall below 1500 kcal/day and 175 g/day, respectively, and there must be an adequate intake of micro- and macro-nutrients to prevent the risk of malnutrition, ketosis and SGAnewborns [65, 93]

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Nutrition after bariatric surgery

Bariatric surgery could be useful for fertile women with severe obesity (BMI above 40 kg/m2 ), who have not responded to dietary and pharmacological treatments.

    Previous bariatric surgery resulting in weight loss is associated with a reduced risk of pre-eclampsia, GDM and LGA newborns [98, 99].

    Nonetheless, increased monitoring during pregnancy is recommended due to a greater risk of maternal anaemia, SGA newborns, preterm delivery, NICU admission and neo-natal mortality [98, 99].

    Evidence suggests that it is advisable for women not to become pregnant until at least 18 months after bariatric sur-gery, once their weight has stabilised and any nutritional deficiencies have been resolved in order to reduce the risk of related neonatal complications [100–103](Table 3).

    According to the guidelines [104, 105], it is advisable to carry out a thorough clinical evaluation and assessment of nutritional status before pregnancy, particularly in women who have lost weight after surgery but remain overweight or obese. It is important to monitor deficiencies in micronutri-ents, in particular Vitamins A, D and B12, potassium, iron, folate, calcium and phosphorus, and to prescribe vitamin and mineral supplements before conception and through-out pregnancy. Folic acid, in particular, must be taken (400 mcg/day, 5 mg/day if obesity persists) at least 1 month before conception and throughout the entire first trimester of pregnancy. Multivitamins containing vitamin A in the form of retinol must be stopped. Macronutrient deficienciesalso need to be checked.

    During pregnancy, foetal growth and weight gain should be monitored and protein intake should not fall below 60 g/ day [104].

    Evidence shows that the correct gestational weight gain is associated with better obstetric outcomes and that IOM recommendations are applicable to pregnant women having undergone bariatric surgery [104].

    A potential side effect of bariatric surgery is dumping syndrome (DS), which is more frequent after gastric bypass (70–75%) or sleeve gastrectomy (40%) and may have the following characteristics:

early onset: 10–30 min after the meal.

late onset: 1–3 h after the meal.

In such cases it is advisable to adjust the diet and advise the patient to eat small, frequent meals, drink liquids 30–60 min before or after the meal, avoid simple sugars and foods rich in simple sugars (sweet, syrups, sugary drinks and fruit juices), increase the intake of fibre, complex carbohydrates and proteins, and avoid alcohol consumption. It may also be useful to takepectin, guar gum and glucomannan to slow down gastric emptying [102, 106].

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Diet in women affected by coeliac disease

Coeliac disease is an autoimmune enteropathy characterised by a chronic inflammatory state of the mucosa of the proxi-mal small intestine. It is a multifactorial pathology resulting

from the interaction between gluten, the immune system, genetic susceptibility and environmental factors [107], and is frequently associated with autoimmune type 1 diabetes.

    In coeliac patients, the aim of a gluten-free diet is to improve the duodenal mucosa and resolve the symptoms; the untreated disease is associated with malabsorption of nutrients. Coeliacs on gluten-free diets, especially women, also have deficiencies of iron, folate, B complex vitamins, calcium and vitamin D. With regard to macronutrients, the CHO intake is reduced and mainly composed of simple sug-ars with a low fibre content, while the fat and protein intake is higher [107, 108].

    In diabetic patients, a gluten-free diet can cause fluc-tuations in blood glucose levels due to impaired intestinal absorption of foods and the high carbohydrate and low fibre contents of many gluten-free foods [107].

    If undiagnosed and untreated, coeliac disease can have negative effects on a woman’s reproductive capacity (amen-orrhea, sterility, miscarriage, increased risk of SGA children and intrauterine mortality). Treatment normalises the out-come of pregnancy. A recent study has shown that coeliac women with GDM more frequently present LGA foetuses, which the authors speculate is because gluten free foods, due to their different composition, influence foetal growth [109].

    In pregnancy complicated by diabetes, difficulties in fol-lowing a gluten-free diet can increase hypoglycaemia, cause nausea and vomiting, slow gastric emptying and cause The limited choice of cereals increases the risk of an inadequate intake of proteins, fats, fibre, calcium, iron, folate and vitamins, so that the use of supplements is often necessary

Vegetarian and vegan diets

Vegetarian diets typically include plant foods and exclude most types of animal-derived foods. There are two main types of vegetarian diets: (1) lacto-ovo-vegetarianism (LOV): meat is excluded, but dairy products, eggs, honey and a wide variety of plant foods are included; (2) vegan-ism (VEG): meat, fish and all animal derived foods such as dairy products, eggs and honey are excluded, while a wide variety of plant foods are included [110–112]. A plant-based diet can be sufficient for a pregnant woman only if well planned so that it provides the recommended requirements for energy and nutrients, such as proteins, fibre, omega-3, fatty acids, zinc, iodine, calcium, vitamin D and vitamin B12. Careful meal planning is necessary to avoid nutritional deficiencies [113, 114]. [Level of evidence I, Strength of recommendation A].

    As the available data are still varied and conflicting, it is essential to seek the help of a specialist in planning any type of diet to ensure the correct physiological development of the foetus [113–119]. A vegetarian diet is not associated with adverse outcomes, such as preterm birth or SGA, as long as all nutritional needs are met. However, plant pro-teins are less digestible than animal proteins, so an increase in dietary protein intake of 20% (up to 1 g/kg/day) is recom-mended [120]. Pregnant women following a vegetarian diet should still follow the recommendations and increase their daily protein intake by 25 g/day to meet the requirements for foetal growth. It is essential that plant foods are integrated with a higher protein intake in the second and third trimester of pregnancy. Protein intake should be increased by at least 10% in pregnant women following a vegan diet [111, 121]. Soya and its derivatives, pseudo-cereals, lupins, spinach and hemp seeds contain all the essential amino acids in similar proportions to animal sources, while legumes, whole grains, nuts and leafy green vegetables are also good sources of protein in vegan diets [111]. [Level of evidence I, Strength of recommendation A]. Since plant foods are rich in fibre which can increase satiety, thus limiting caloric intake andinterfering with nutrient absorption, it is useful to substitute products such as hulled legumes, refined cereals, fat-free or skimmed soya milk and yoghurt with unhulled legumes, whole-grain cereals and full-fat soya milk and yoghurt [122]. The pregnant woman’s diet should include two daily portions of foods rich in omega3 to satisfy DHA needs, but since conversion of ALA to PUFA may be insufficient, all pregnant women, especially if they follow a vegetarian or vegan diet, should take a supplement of 100–200 mg of DHA each day [123]. DHA of algal origin is a valid alter-native for vegan women. Vegan and vegetarian diets have a higher iron content than an omnivorous diet. However, the iron in plant foods is the non-haeme form, which is less well absorbed than the haeme iron found in meat, fish and derivatives (1–34% and 15–35% bioavailability, respectively) [124]. Iron-rich foods should be consumed daily and-combined with a source of vitamin C, which increases the bioavailability of non-haeme iron. Iron supplementation is required when haemoglobin levels fall below 110 g/l dur-ing the first trimester or below 105 g/l during the second and third trimesters of pregnancy [124]. Calcium needs can be met with a lacto-ovo-vegetarian diet during pregnancy, but also with a vegan diet by consuming vegetables rich in calcium and bicarbonate-calcium mineral waters (300– 350 mg/l) [111]. However, vegetarian and vegan women are at risk of vitamin D deficiency: plant sources of this vitamin are beans, broccoli and leafy green vegetables, but the content, and hence the intake, is low, necessitating a supplement of 25(OH)D to meet the increased needs of pregnancy (the recommended dose is 1000–2000 IU/day) [111]. Finally, vitamin B12 deficiency can occur during pregnancy regardless of the type of diet, due to the depletion of reserves caused by an increased demand for this micronu-trient [125, 126]. Since the consumption of plant foods can-not meet vitamin B12 requirements, it is recommended that all pregnant vegetarian and vegan women are monitored, if possible from before pregnancy, and are given a supplement either orally or parenterally.

Nutraceuticals and hyperglycaemia in pregnancy: inositol and probiotics

In recent years, there has been growing interest in the role of nutraceuticals in the prevention and treatment of hypergly-caemia in pregnancy. These nutraceuticals are nutrients and/ or bioactive compounds that are contained in some foods, especially those of plant or microbial origin, and that have beneficial effects on human health. The focus has, in par-ticular, been on inositol and probiotics (128).

    Inositol is a polyol naturally present in animal and plant cells. In nature, it is found in nine isomeric forms, the most frequent being myo-inositol (MI) and D-chiro-inositol (DCI), which have proven insulin-mimetic properties and efficiency in improving glycaemic control, particularly post-prandial, which is of particular importance during pregnancy, a period of a woman’s life characterised by insu-lin resistance [127].

    Women with GDM have been found to have higher urinary excretion of inositol and its metabolites and low plasma concentrations of inositol. Much research has there--fore focused on the possible role of inositol in the preven-tion and treatment of GDM [127–140]. Various studies on women with a family history of diabetes or obesity who were treated with inositol have shown a reduction in the devel-opment of GDM and favourable neonatal outcomes, while preterm births were reduced and lower glycaemic values were reported during oral glucose tolerance tests (OGTT) in women at risk. On the other hand, no recommendations have so far been made regarding the use of MI in women of reproductive age for the prevention of GDM; further multi-centre randomised trials with larger populations of different ethnicities are needed, and diet, exercise and pharmacologi-cal interference also need to be evaluated [138].

    Given these premises and the potential beneficial action of myo-inositol on blood glucose, the Position Statement of the AMD-SID and the Interassociative Diabetes and Preg-nancy Study Group suggests using MI at a daily dose of 4000 mg in the prevention of GDM in Caucasian women [Level of evidence I, Strength of recommendation B] [141]. Continuous monitoring has shown MI to be effective in reducing glycaemic variability. MI has also been shown to be safe and without side effects at higher doses (4000 mg/3 times daily) in GDM pregnancies and to have a more rapid hypoglycaemic effect, opening up new therapeutic perspec tives in treatment [142, 143]. A recent Cochrane review confirmed that prenatal supplementation with myo-inositol is potentially beneficial in reducing the incidence of GDM [144]. MI at a dose of 4000 mg per day can be used to treat GDM in Caucasian women alongside medical nutrition therapy and lifestyle interventions [Level of evidence II, Strength of recommendation B].

    Research has recently also focused on probiotics, food components or ingredients fermented by intestinal bacterial flora that can benefit the host by selectively promoting the growth and/or activity of one or more of the bacterial spe-cies already present in the intestinal tract.

    There are numerous critical issues surrounding evalu-ation of the preventive or therapeutic effects of probiotic supplementation that are related to sample size, method-ologically different approaches and the different strains of microorganisms studied. The microbiota is influenced by several factors: the interaction between the environment and diet, individual genetic make-up and the microbial strains that make up the microbiota itself. Disorders of maternal metabolism can lead to an imbalance in the microbiota, or dysbiosis, which has been shown to increase the risk of pre-eclampsia, diabetes, infection and preterm birth. Neonatal gut dysbiosis also appears to play a significant role in dis-ease processes and long-term metabolic health [145].

    The administration of specific probiotics that modulate the gut microbiome during pregnancy seems to improve insulin sensitivity [146] by modulating the anti-inflamma tory response [147] and upregulating the genes involved in fat metabolism and insulin sensitivity [147, 148]. Supple-mentation with probiotics could, therefore, be effective in improving insulin resistance, preventing GDM and obesity, and improving neonatal outcomes [149–156]. However, the data from these studies are extremely controversial and have not been confirmed by other studies [155–158].

    Recent Cochrane reviews [159, 160] of studies of over-weight and obese women showed that treatment with probi-otics affected the risk of GDM compared with a placebo. An increased risk of pre-eclampsia was reported but no other maternal-foetal outcomes were affected. On the other hand, other systematic reviews have found a reduction in insulin resistance (HOMA-IR) and improvements in insulin secre-tion (HOMA-B) and the QUICKI index compared with a placebo, as well as reductions in inflammatory markers and interleukin, and a slight effect of supplementation on triglyceride and total cholesterol levels [161, 162]. More recently, the Nutritional Intervention Preconception and During Pregnancy to Maintain Healthy Glucose Levels and Offspring Health (NiPPeR) study group carried out a multicentre, double-blind, randomised controlled trial [163] with 1,792 women. They evaluated the impact of myo inositol, micronutrients (vitamins D, B6 and B12, ribofla-vin and zinc) and probiotics taken before the beginning of pregnancy on the control of blood sugar during pregnancy and more generally on the health of pregnant women and their offspring. The results showed no significant effects on the incidences of GDM and LGA infants, but a reduction inpreterm births, confirming the results of previous studies. Interestingly, the NiPPeR study also investigated the impact of maternal, preconception and prenatal nutritional supple-mentation with myo-inositol, probiotics and additional micronutrients on offspring outcomes monitored from birth to 2 years of age and found that the supplementation was associated with a lower risk of rapid childhood weight gain and obesity in the offspring at 2 years of age.

    Given the inconsistency of the published results, we conclude that there is no evidence to confirm the efficacy of probiotics in the prevention or treatment of GDM. The inconsistency is due to several factors, including varying durations of treatment, different single or multiple strains of probiotics, differences in the quantities administered and in the periods of the pregnancy in which the probiotics were

Breastfeeding

International and Italian guidelines recommend breastfeed-ing in the first 6 months of life [164–167] highlighting the importance of correct nutrition on the part of the mother during the breastfeeding period [167–169].

    The nutritional and energy demands of breastfeeding are even greater than those of pregnancy itself. Breastfeed-ing women require an average of 500 kcal more than their usual requirement, an increase that is related to the volume (mean 780 ml) and energy content of the milk secreted (67 kcal/100 ml) [170, 171] [Level of evidence VI, Strength of recommendation A]. LARN 2024 [37] recommends an additional 330 Kcal/day in the first 6 months of breastfeed-ing (around 170 kcal should come from maternal energy reserves resulting in a weight loss of 0.5–1 kg/month from the second month postpartum onwards) and 400 kcal in the following months when milk production is reduced to around 600 ml/day [Level of evidence I, Strength of recom-mendation A].

    Without undermining WHO recommendations on the importance of breastfeeding [165–167], the use of con-ventional formula milks (largely derived from cow’s milk) results in a greater weight gain in the first year of life and beyond compared with breastfeeding [167, 168, 171]. This effect is probably due to the greater protein content of cow’s milk, which in turn determines greater post-prandial hyper-aminoacidemia in the newborn and increased secretions of insulin, growth hormone and IGF [171–173]. The resulting accelerated growth of the child could also be associated with a greater risk of obesity and metabolic diseases [171, 172]. Artificial milks have therefore been developed (derived, in particular, from cow’s milk) with a reduced protein content and a composition similar to that of breast milk.

    During breastfeeding, it is recommended in that the daily protein intake be increased from the pre-pregnancy amount of ≈0.8 g/kg to at least≈1.1 g/kg, equivalent to +18–25 g/ day of protein [37, 173] [Level of evidence I, Strength of recommendation A].

    A greater increase in protein in the first semester than in the following months is recommended (+21 g/day com-pared with +14 g/day). The minimum protein requirement for mothers with a good nutritional status who have recently given birth is the same as FDA recommendations (≈1, 0 g/ kg), and is also similar to the average intake of the Italian population (1.1–1.2 g/kg). In lean and/or relatively mal-nourished women, on the other hand, the protein require-ment may be higher than ≈1.1 g /kg/day, particularly if the protein sources of their diet are predominantly plant based.

    Lipid intake during breastfeeding can affect the new-born’s growth, development and health[ 174] [Level of evidence VI, Strength of recommendation A]. It should be much the same as the general population’s intake [174], and this also goes for carbohydrate intake (50–55% of total energy intake, about 80–90% of which should be complexcarbohydrates) [175, 176].

    Regarding micronutrients, the European Micronutrients Recommendations Aligned (EURECCA) project [170, 177, 178] aims to harmonise dietary recommendations. A higher intake of vitamins A, B1, B2, B6, B12 and C, and folates is recommended during breastfeeding [170]. Most of the cal- cium used for milk synthesis is mobilised from the maternal skeletal system, which replenishes its losses during wean-ing, so calcium supplementation during breastfeeding is not recommended [37] [Level of evidence I, Strength of recom-mendation A]. Many breastfeeding women have a vitamin D deficiency, a risk factor for osteomalacia (in the mother), rickets (in the newborn) and impaired skeletal growth of the child. However, there are no firm data on the effects of vitamin D deficiency on foetal and maternal peri-partum complications, but they are clear on the effects on maternal infectious diseases [178] [Level of evidence VI, Strength of recommendation A].

   In some European countries, an approximately 35% increase in dietary iodine intake is recommended during breastfeeding to prevent iodine deficiency in the post-par-tum period due to changes in maternal iodine metabolism as a function of milk secretion [179, 180] [Level of evidence VI, Strength of recommendation A]. Iodine levels in the breast milk mainly depend on the amount of dairy milk con-sumed by the mother (recommended iodine intake 250 µg per day). While the optimal iodine content in breast milk is 100–150 µg/dl, more than 75 µg/L is generally sufficient, but less than 30 µg/L in iodemia can result in areas with endemic goitre [181, 182] if maternal intake is inadequate.

    Obese mothers start breastfeeding later and stop earlier than normal weight mothers [183, 184]. Maternal obesity can slow prolactin secretion, altering the transfer of milk to the newborn.

    Women having undergone bariatric surgery are encour-aged to breastfeed for at least 6 months, and their plasma micronutrient concentrations should be periodically moni-tored. In women who have undergone gastric banding, it is advisable to deflate the band until breastfeeding actu-ally begins. The increased risk of infants of obese mothersdeveloping obesity can be reduced by breastfeeding [184].

    Diabetes does not contraindicate breastfeeding, but dia-betic women have greater difficulty beginning and main-taining breastfeeding than other women. Good metabolic control is essential to breastfeeding [185].

    As vegetarian and vegan diets are highly varied, a criti-cal evaluation of the diets of breastfeeding woman follow-ing these regimes must be carried out. In general, Vitamin D supplements are recommended for women who do not consume dairy milk, and B12 supplements (2.6 µg/day) for ovo-lacto-vegetarians and vegans [110]. Calcium may also be deficient in these diets, so a supplement bringing the intake to 1200–1500 mg/day is recommended [37]). Where the diet includes fish, it is advisable to avoid types that may be contaminated with high levels of mercury.

Conclusions

Good nutritional status is essential for healthy pregnancy and to reach this aim these recommendations, an update of a previous version about the MNT for pregnant women performed in 2014 have taken into consideration the most recently published data on nutrition in physiological pregnancy and pregnancy complicated by hyperglycaemia and/or obesity. In particular new evidences on the correct weight gain and carbohydrate intake in patients with GDM and obese have been inserted and discussed. Furthermore a chapter on nutrition after bariatric surgery and on nutraceu-ticals in pregnancy: inositol and probiotics have ben added. However some gaps in nutrition during pregnancy persists, data from recent papers underline the necessity to review the weight gain recommendations of the IOM because there are to liberal in obese and morbid obese women, however there no international consensus; the same is for the correct caloric and carbohydrate intake in GDM, type 2 and obese pregnant women.Finally women who have undergone bar-iatric surgery consitute a problem in terms of correct nutri tion during pregnancy when affected by dumping syndrome but no specific guidelines have yet been produced and this constitute a problems for the specialist who follow them.

 This article is excerpted from the 《Acta Diabetologica》 by Wound World.