An updated review of popular dietary patterns during pregnancy and lactation: Trends, benefits, and challenges

Abstract

This review examines nutritional needs during pregnancy and lactation, focusing on the critical nutrients required for both maternal and fetal health. Essential nutrients such as folic acid, vitamin D, iron, calcium, and omega-3 fatty acids play a significant role in supporting fetal development and minimizing the risk of complications like gestational diabetes, hypertension, and preterm birth. Various dietary patterns, including the Mediterranean, vegetarian/vegan, and gluten-free diets, were evaluated for their adequacy and potential benefits. The Mediterranean diet was highlighted for its protective effects against pregnancy-related health issues. In contrast, the review identified vegetarian and vegan diets as requiring careful planning to ensure sufficient intake of key nutrients. Additionally, the review explored the implications of gestational diabetes and dietary strategies for managing blood sugar levels. The effects of intermittent fasting during pregnancy were also discussed, with mixed evidence regarding its safety and impact on pregnancy outcomes. Overall, the review stresses the importance of tailored nutritional guidance to ensure optimal health for both the mother and the developing fetus during pregnancy and lactation.

Highlights

• •Vegan/vegetarian diets are safe in pregnancy if well-planned with attention to key nutrients.
• •Mediterranean diet improves pregnancy outcomes, reducing risks like gestational diabetes.
• •Ketogenic diet safety is unclear in pregnancy due to potential nutrient deficiencies.
• •Diabetic diets are crucial for managing blood sugar and reducing pregnancy complications.
• •Intermittent fasting safety in pregnancy is unconfirmed; less suitable for expectant mothers.

Abbreviations

WHO

World Health Organization

FDA

Food and Drug Administration

ACOG

American College of Obstetricians and Gynecologists

NIH

National Institutes of Health

NHS

National Health Service

CDC

Centers for Disease Control and Prevention (CDC)

BNF

British Nutrition Foundation

BDA

British Dietetic Association

EPA

eicosapentaenoic acid

DHA

docosahexaenoic acid

RDA

Recommended Daily Allowance

1. Introduction

Pregnancy and lactation are critical periods during which nutritional requirements undergo significant changes to support both maternal health and fetal development. The nutrients consumed during these phases are essential for proper growth, immune function, and the prevention of potential complications such as gestational diabetes, preterm birth, and developmental delays. With the evolving prevalence of pregnancy-related health conditions and dietary preferences, it is crucial to gain a deeper understanding of how different dietary patterns influence maternal and fetal health. Traditional dietary models, such as the Mediterranean diet, are often recommended due to their well-documented benefits for both mother and child. However, alternative diets, including vegetarian, vegan, and gluten-free diets, have gained popularity, necessitating a closer look at their nutritional adequacy during pregnancy and lactation. Moreover, with the rising prevalence of gestational diabetes, understanding how specific diets can help manage blood sugar levels is crucial for preventing long-term health complications [[1], [2], [3], [4], [5]]. This review aims to explore the necessary nutrients for pregnancy and lactation, evaluate various dietary patterns for their efficacy, and provide guidance on how to meet nutritional needs during these vital life stages.

2. Purpose

The purpose of this article is to explore the impact of various dietary patterns during pregnancy, focusing on their nutritional benefits and implications for maternal and fetal health. Specifically, it examines the Mediterranean diet, diabetic diet, and intermittent fasting, highlighting their role in managing blood sugar levels, reducing pregnancy complications, and promoting optimal fetal development. The article aims to provide insights into how different dietary approaches can support a healthy pregnancy, offer practical recommendations for healthcare professionals, and emphasize the importance of personalized nutrition during this critical period. Furthermore, it addresses the challenges and benefits of adopting specific diets for individuals with health conditions like gestational diabetes or gluten intolerance during pregnancy and lactation, stressing the need for tailored guidance and monitoring.

2.1. Methodology

This review was conducted through a comprehensive search of scientific literature using the following academic databases: PubMed, Google Scholar, ScienceDirect, Scopus, and Web of Science. We also searched the grey literature and conference proceedings. The focus was on identifying articles related to the essential nutrients required during pregnancy and lactation, including the necessary quantities and their role at each stage of these periods. Additionally, studies were reviewed on various dietary patterns, their limitations, the "rules" they impose, and their adequacy and health benefits during pregnancy and lactation. The search also included guidelines and recommendations from reputable organizations and websites, such as the World Health Organization (WHO), the U.S. Food and Drug Administration (FDA), the American College of Obstetricians and Gynecologists (ACOG), the National Institutes of Health (NIH), the National Health Service (NHS), the Centers for Disease Control and Prevention (CDC), the American Pregnancy Association, the Cochrane Library, Mayo Clinic, the British Nutrition Foundation (BNF), the British Dietetic Association (BDA), WebMD, Johns Hopkins Medicine, UW Medicine, and MedlinePlus.

2.1.1. Inclusion and exclusion criteria

Inclusion criteria were the following: a) Studies must be peer-reviewed and published in English; b) Research should focus on dietary patterns during pregnancy and/or lactation; c) Articles should address at least one of the following: maternal health, fetal development, or nutritional adequacy; d) Studies examining the role of specific nutrients (e.g., folic acid, vitamin D, iron) within dietary patterns and e) Guidelines or recommendations from reputable health organizations.

Exclusion Criteria were the following: a) Studies not related to human pregnancy or lactation; b) Articles not available in full text or with insufficient methodological details; c) Research focusing solely on non-dietary interventions and d) Studies with small sample sizes or high risk of bias, as determined by standardized assessment tools.

2.2. Search strategy

The MeSH keywords in PubMed included the following: Pregnancy Nutrition OR Lactation Nutrition OR ("Dietary Patterns"[Mesh] OR "Maternal Nutrition"[Mesh]) OR ("Pregnancy Complications/etiology"[Mesh] OR "Fetal Development/nutrition effects"[Mesh] OR "Diet, Mediterranean"[Mesh] OR "Diet, Vegetarian"[Mesh] OR "Nutritional Status"[Mesh] OR "Gestational Diabetes/nutrition therapy"[Mesh] OR "Micronutrients"[Mesh] OR "Omega-3 Fatty Acids"[Mesh] OR "Calcium"[Mesh] OR "Iron"[Mesh] OR "Folic Acid"[Mesh] OR "Vitamin D"[Mesh]).

The keywords on other databases included the following: pregnancy nutrition, lactation nutrition, maternal dietary requirements, Mediterranean diet, vegetarian diet, vegan diet, ketogenic diet, gluten-free diet, intermittent fasting, gestational diabetes, maternal health, fetal development, placental function, dietary patterns, nutrient deficiencies, omega-3 fatty acids, vitamin D, folic acid, calcium, iron, blood sugar regulation, low glycemic index diets, healthy eating during pregnancy, pregnancy-related complications, personalized nutrition, dietary adequacy, preterm birth, low birth weight, hypertension in pregnancy, and nutrient supplementation during pregnancy.

3. Results

The review identified several key findings regarding the nutritional requirements during pregnancy and lactation. Essential nutrients such as folic acid, vitamin D, iron, calcium, and omega-3 fatty acids were highlighted as crucial for supporting maternal health and fetal development. Adequate intake of these nutrients plays a vital role in preventing complications such as preterm birth, gestational diabetes, hypertension, and intrauterine growth restriction. Furthermore, specific dietary patterns were examined, including the Mediterranean diet, vegetarian/vegan diets, and gluten-free diets, with each offering distinct advantages and challenges. The Mediterranean diet, for instance, was found to provide protective benefits against conditions like asthma, allergies, and gestational diabetes, while also improving placental blood flow, thereby reducing the risk of low birth weight and preterm birth. In contrast, while vegetarian and vegan diets can be nutritionally sufficient, careful planning is required to ensure adequate intake of certain nutrients, such as vitamin B12, iron, and omega-3 fatty acids. The review also discussed the increasing prevalence of gestational diabetes and the importance of tailored dietary plans for individuals with this condition. It was noted that balanced meal timing and the inclusion of low-glycemic-index foods were key to managing blood sugar levels effectively. Finally, the intermittent fasting pattern was explored, with mixed findings regarding its impact on pregnancy. While some studies suggested potential benefits in glucose regulation, caution was advised due to concerns over its possible effects on birth outcomes, such as low birth weight and preterm delivery. Overall, the findings emphasized the importance of personalized nutrition and the role of healthcare professionals in guiding dietary choices during pregnancy and lactation to ensure optimal outcomes for both mother and child.

4. Nutritional needs during pregnancy

4.1. Protein

Protein is a fundamental component of a healthy diet, essential for supporting both growth and maintenance [1].

During pregnancy and lactation—periods characterized by rapid growth and the maintenance of maternal and fetal structures—adequate dietary protein intake is crucial for a healthy outcome. The current definition of protein requirements for pregnant or lactating individuals states that "they must meet the needs associated with tissue deposition or milk secretion at rates consistent with good health" [2].

The additional protein consumed during pregnancy is estimated to be allocated approximately 40 % to the fetus, placenta, and amniotic fluid, while the remaining 60 % supports maternal physiological changes such as the growth of the uterus, breast, and fat tissues, as well as the increase in blood volume and extracellular fluid [1]. It is essential to understand that the extra energy required during pregnancy is not evenly distributed across trimesters. It is almost negligible during the first trimester, increases during the second one, and peaks during the third trimester. For this reason, recommendations should be individualized according to the stage of pregnancy and the specific needs of the mother and fetus.

For individuals who are not pregnant, protein intake should comprise 10–35 % of daily dietary intake, amounting to 71 g/day. During the first trimester, daily intake should increase by just 1 g/day, by 8 g/day in the second trimester, and by 26 g/day during the third trimester and lactation [3].

4.2. Carbohydrates

Carbohydrates are one of the primary nutrients, consisting of fiber, starch, and sugars. When consumed, the body converts carbohydrates into glucose, which provides the necessary energy for complex physiological processes. In a healthy individual, this energy is utilized by the body's cells, tissues, and organs However, energy needs to increase during pregnancy to support the developing fetus—particularly its brain—and the placenta, which relies on maternal glucose to the same extent as the mother's brain [4]. The recommended daily intake of carbohydrates during pregnancy and lactation is 175 g/day [4,5].

It is important for pregnant individuals to choose carbohydrate sources with a low glycemic index, such as whole grains, fruits, starchy vegetables, and beans, rather than foods high in sugar like, honey, and syrups, which should be limited [5].

4.3. Fats

Fats are an essential component of a healthy diet during pregnancy and lactation. They serve three primary roles: providing energy, aiding in the transport of fat-soluble vitamins (A, D, E, and K), and producing essential fatty acids that the body cannot synthesize on its own [5].

There are no specific guidelines for daily fat intake during pregnancy beyond those for non-pregnant individuals, which recommend that fats comprise 25–35 % of total calories [5].

However, it is advised to avoid foods rich in trans and saturated fats and minimize animal fat intake, as these are linked to an increased risk of gestational diabetes. Emphasis should be placed on foods high in EPA and DHA [5].

4.4. Omega-3 fatty acids

Omega-3 fatty acids are essential fats that the body cannot synthesize on its own and must be obtained through diet or supplements [6].

Research has shown that Omega-3 intake during pregnancy improves fetal neurological development, as demonstrated through various tests on problem-solving, language development, and more [6]. Additionally, adequate Omega-3 levels help maintain low levels of prostaglandins, reducing the risk of preterm birth [7,8].

The FDA and subsequently the ACOG recommend consuming two servings of fish per week, equivalent to 200–300 mg/day, for both pregnant and lactating individuals [6].

4.5. Iron

Iron plays a vital role in hemoglobin synthesis and oxygen transport [4,9]. In pregnancy, the maternal body requires more iron to support the increased blood volume, as well as the development and maintenance of the fetus and pregnancy structures (e.g., placenta). To meet this demand, intestinal iron absorption increases from 10 % to 40 % in the third trimester [9].

A mother's pre-pregnancy iron stores are a critical predictor of potential iron deficiency during pregnancy. Maintaining normal iron levels is crucial for both the developing fetus and the mother, as iron deficiency and low hemoglobin levels are responsible for 20 % of maternal deaths worldwide [10]. For pregnancy outcomes, studies indicate that iron deficiency is associated with risks of preterm delivery, low birth weight, and increased neonatal morbidity [11]. The most common cause of iron deficiency is a poor diet with insufficient iron-rich foods. Secondary causes include intestinal parasites and chronic blood loss.

The Recommended Daily Allowance (RDA) for iron increases from 18 mg/day in non-pregnant women to 27 mg/day during pregnancy [12]. During lactation, it decreases to 8 mg/day [13].

4.6. Folic acid

Vitamin B9, more widely known as folic acid, plays a crucial role in DNA synthesis and neurotransmitter production [14]. Its importance extends further as it significantly contributes to protein synthesis, amino acid metabolism, and cell multiplication, making it indispensable during the initial weeks of fetal life [15].

Folic acid is essential for the formation of the brain and the neural tube, which closes by the 4th week of pregnancy. Its deficiency, which is not uncommon, may lead to severe complications, including spina bifida (an opening in the lower part of the neural tube) and anencephaly [15].

Therefore, it is recommended that individuals planning a pregnancy take 400 μg/day of folic acid for at least three months prior to pregnancy and continue with the same dose throughout pregnancy, as advised by the FDA [16,17]. Its intake should continue until at least the 12th week of pregnancy.

4.7. Iodine

During pregnancy, iodine requirements increase due to a 50 % rise in maternal production of the thyroid hormone T4 [9]. This occurs because the fetal thyroid function begins between the 10th and 12th week of gestation and becomes fully established around the 18th to 20th week. Until then, the fetus relies on the maternal production of T4, which is directly proportional to the iodine intake of the mother. Reduced iodine intake leads to decreased T4 production [18].

This is crucial because the thyroid hormone is necessary for the proper development of the fetal brain and intelligence, with research suggesting an IQ drop of up to 20 points in cases of iodine deficiency. Additionally, iodine deficiency can result in fetal goiter, hypothyroidism, and cretinism [18,19].

The World Health Organization (WHO) recommends a daily iodine intake of 220–250 μg during pregnancy and lactation [20].

4.8. Vitamin B12

Vitamin B12 is a water-soluble vitamin synthesized exclusively by microorganisms and obtained through the consumption of animal products such as meat, eggs, and dairy [15]. It is vital for maintaining healthy blood and nerve cells.

Deficiency of B12 is not uncommon during pregnancy. Low levels of B12 are associated with increased risks of certain complications, including miscarriage, intrauterine growth restriction, brain and spinal cord problems, and vitamin deficiency in the infant [21].

The recommended daily intake is 2.6 μg/day during pregnancy and 2.8 μg/day during lactation, compared to 2.4 μg/day for non-pregnant women [13].

4.9. Calcium

Calcium is an essential nutrient involved in various physiological processes, most notably bone mineralization and its role as a key intracellular component in maintaining cellular membranes [14].

During pregnancy, calcium is actively transferred to the fetus through the placenta, particularly during the third trimester, when demands are higher [14]. The maternal body compensates by doubling intestinal absorption of calcium and mobilizing it from maternal bones [14]. However, these adaptations are not always sufficient. It is recommended that individuals during pregnancy increase their dietary calcium intake to 1000–1200 mg/day, especially during the third trimester [9,22].

Calcium deficiency has been linked to hypertensive disorders, preeclampsia [15], osteopenia, muscle cramps, and tremors in the mother. For the fetus, inadequate calcium can result in poor growth and low birth weight.

4.10. Magnesium

During pregnancy, maternal serum magnesium levels gradually decrease, reaching their lowest point during the third trimester, and begin to rise again after delivery [9]. High levels of magnesium detected in the umbilical cord compared to maternal serum reveal active transfer to the fetus through the placenta, with 50 % of dietary magnesium intake being absorbed [9]. The increased demands during pregnancy are normally balanced by a 25 % rise in renal magnesium excretion [23]. Nevertheless, dietary intake must also be increased.

Magnesium deficiency during pregnancy has been linked to hypertensive disorders, gestational diabetes, preterm labor, and intrauterine growth restriction [24]. The recommended magnesium intake during pregnancy is 350–400 mg/day, while during lactation, it ranges from 310 to 360 mg/day [24].

4.11. Vitamin D

Vitamin D is an essential fat-soluble vitamin and prohormone. It exists in two forms: ergocalciferol (D2), synthesized by plants, and cholecalciferol (D3), synthesized by animals and the human body when exposed to sunlight [9,14,24]. Regardless of the source (dietary or through sunlight), vitamin D undergoes further processing in the liver and kidneys to form its active version, 1,25-dihydroxyvitamin D [9].

This active form plays a critical role in calcium homeostasis and, consequently, in the proper development of fetal bones and teeth [12,25]. Vitamin D deficiency during pregnancy has been associated with neonatal osteoporosis, childhood rickets, low birth weight [26], cardiac failure, and an increased risk of low bone density. For mothers, severe deficiency can lead to symptomatic osteomalacia during pregnancy [14,27].

Adequate intake of vitamin D reduces the risk of preeclampsia and preterm labor [14,28]. Deficiency risk increases for women living in regions with low sunlight exposure, particularly during fall and winter, and is higher in women with darker skin, as absorption is less efficient than in women with lighter skin tones [29,30].

The recommended daily intake of vitamin D is 10–15 μg/day (400–600 IU/day) during the first two trimesters, increasing to 1000 IU/day in the third trimester [9].

5. Dietary patterns

5.1. Vegetarian diets

5.1.1. Veganism

In recent years, veganism has become increasingly popular, with 3 % of the population reportedly following this diet [31].

The official definition by the Vegan Society states:

"Veganism is a philosophy and way of living which seeks to exclude—as far as is possible and practicable—all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose; and by extension, promotes the development and use of animal-free alternatives for the benefit of animals, humans and the environment. In dietary terms it denotes the practice of dispensing with all products derived wholly or partly from animals." [32].

Regarding diet, vegans exclude all meat, fish, dairy products, eggs, honey, and any other animal-derived foods.

Strict vegetarians adhere to a comparable dietary framework, eliminating all animal-derived products from their consumption. However, they do not necessarily embrace the broader ethical philosophy associated with veganism, particularly in relation to non-dietary items such as clothing and cosmetics [33,34].

By avoiding these foods, there is an increased risk of deficiencies in essential nutrients such as protein, iron, vitamin D, calcium, iodine, omega-3 fatty acids, and vitamin B12 [35]. However, existing evidence supports that a well-planned vegan diet, with awareness of the levels of these nutrients, is safe during both pregnancy and lactation.

When discussing a vegan diet, the focus is often on its deficiencies and the exclusion of certain foods. However, we should not overlook its richness in other dietary categories, such as grains, legumes, fruits, vegetables, nuts, and herbs.

Pregnant and breastfeeding mothers following a vegan diet should meet specific criteria to ensure a healthy pregnancy outcome. These criteria are as follows [36,37]: a) Consume a large variety of plant-based foods, preferably unprocessed. A vegan diet can be nutritionally adequate when caloric needs are met through nutrient-dense plant foods. However, during late pregnancy, fiber intake should be limited; b) Limit the quantity of plant-based fats, as recommended by Dietary Reference Intakes (DRIs) to avoid replacing more nutrient-dense foods and to limit excessive calories. Selective choices of plant-based fats, such as omega-3 fatty acids and monounsaturated oils, are encouraged, while trans fats and tropical oils should be avoided; c) Ensure adequate calcium intake and prioritize vitamin D consumption. While good plant-based sources of calcium should be included, vitamin D intake recommendations align with those of the general population, as no dietary pattern can fully meet vitamin D requirements; d) Ensure adequate vitamin B12 intake. Adequate sources of vitamin B12 are fundamental to a well-planned vegan diet, as levels can easily become compromised in individuals following this dietary pattern.

Good sources of protein include legumes, grains, nuts, seeds, green leafy vegetables, soy and soy products, quinoa and seitan [37].

It is important to note that all essential amino acids are found in plant-based protein sources [37]. Foods rich in these include soy, quinoa, buckwheat, amaranth and spinach.

Carbohydrates are primarily obtained from potatoes, bread, grains, rice, and pasta [38]. Healthy fats are found in olive oil, avocado, and specific nuts such as almonds, peanuts, and Brazil nuts [39]. Rich sources of omega-3 fatty acids include plant oils, flaxseed oil, chia seeds, hulled hemp seeds, and walnuts [37,40]. Iron is abundantly available in legumes, whole grain flour and bread, iron-fortified cereals, dark green leafy vegetables such as broccoli, nuts, and dried fruits like apricots, prunes, and figs [37,40]. Folic acid can be sourced from broccoli, Brussels sprouts, green leafy vegetables such as cabbage and spinach, peas, chickpeas, beans, and cereals fortified with folic acid [41].

Iodised salt, recognized as the safest source, and sea vegetables such as seaweed are excellent sources of iodine [37]. Vitamin B12 can be obtained from fortified cereals, unsweetened fortified soy beverages, yeast extract, and nutritional yeast enriched with vitamin B12 [37,40]. Calcium is abundantly found in green leafy vegetables, such as broccoli, cabbage, and okra, though not in spinach due to limited calcium absorption. Other notable sources include unsweetened fortified soy, pea, and oat beverages, tofu, sesame seeds, tahini, legumes, and dried fruits such as raisins, prunes, figs, and apricots [37,40]. Magnesium is commonly present in spinach, nuts, and whole grain bread [42]. Vitamin D is primarily synthesized through sun exposure, particularly between late March and late September, with precautions to avoid sunburn. Additional sources include fortified cereals and unsweetened soy beverages enriched with vitamin D [37,40].

5.1.2. Vegetarianism

A vegetarian is defined as an individual who abstains from consuming meat, poultry, fish, and other animals, while still consuming animal-derived products such as eggs and dairy, distinguishing it from veganism [43]. Approximately 5 % of the global population adheres to a vegetarian diet [33].

A well-planned vegetarian diet can effectively meet the increased nutritional demands of pregnancy, providing sufficient calories and nutrients. Similar to veganism, numerous reviews have demonstrated that a vegetarian diet is safe during pregnancy when nutritional requirements are carefully considered [44]. Studies indicate that, with adequate access to appropriate foods, there are no significant differences in pregnancy duration or infant birth weight between vegetarian and non-vegetarian mothers. However, some research has observed slight reductions in neonatal anthropometric measurements, likely due to the lower pre-pregnancy BMI of vegetarian mothers and reduced weight gain during pregnancy. Additionally, a vegetarian diet combined with physical exercise may lower the risk of preeclampsia, while high fiber intake is beneficial in preventing gestational diabetes. The evidence regarding preterm birth outcomes, however, remains inconclusive [44].

Vegetarian mothers are capable of producing breast milk with a nutrient composition comparable to that of non-vegetarian mothers, supporting adequate infant growth [45].

The essential nutrient sources for vegetarians align closely with those recommended for vegans, with the inclusion of eggs and dairy products. Eggs are a rich source of protein [40], omega-3 fatty acids [40,46], iodine [47], vitamin B12 [40,41], and vitamin D [48]. Similarly, dairy products provide excellent sources of protein [40], iodine [47], calcium [49], and vitamin B12 [40,41].

5.1.3. Other vegetarian diet variations

5.1.3.1. Ovo-vegetarian

Includes eggs but excludes meat, poultry, seafood, and dairy products [50].

5.1.3.2. Lacto-vegetarian

Includes dairy products but excludes meat, poultry, seafood, and eggs [50].

5.1.3.3. Lacto-ovo-vegetarian

Includes both eggs and dairy products but excludes meat, poultry and seafood [51].

5.1.3.4. Pescatarian

Includes seafood, eggs, and dairy products but excludes all other meats [52]. About 3 % of the population follows this diet [33].

5.1.3.5. Fish

Provides good sources of protein [40], fats [39], omega-3 fatty acids [52], iodine [47], vitamin B12 [41], and vitamin D [48].

5.1.3.6. Flexitarian

Includes all food groups mentioned above, including meat, but in small quantities or occasionally [50]. About 14 % of the population follows this diet [33]. Meat and poultry can serve as accessible sources of protein [53], iron [54], vitamin B12 [41], and vitamin D [48].

All types of vegetarian diets are considered safe during pregnancy, provided the recommended dietary intakes of key nutrients are met.

5.2. Ketogenic diet

The ketogenic diet is a nutritional approach characterized by low carbohydrate and high-fat intake. It primarily aims to promote weight loss, enhance mental clarity, and boost energy levels. This unique macronutrient distribution induces a metabolic state called ketosis, during which the body uses fat instead of carbohydrates as its primary energy source [55].

The macronutrient breakdown is as follows: a) 55%–60 % fats; b) 30%–35 % proteins and c) 5%–10 % carbohydrates. For example, in a daily intake of 2000 calories, the allowable carbohydrate quantity ranges between 20 and 50 g.

Historically, the ketogenic diet was first introduced in 1921 as a treatment for epilepsy [56]. In subsequent years, especially during the 1970s, it gained recognition as a potential therapy for various other conditions, including Type 2 Diabetes in obese patients [57]. Additionally, it has been studied as a complementary approach in some cancer treatments and is thought to aid in addressing certain neurodegenerative diseases and neuromuscular disorders [58]. Recent research also suggests potential benefits in reducing hyperlipidemia and cardiovascular diseases [59].

To date, there is insufficient evidence to confirm the safety of the ketogenic diet during pregnancy. Even outside pregnancy, this dietary model can be challenging to follow due to the carbohydrate content of staple foods like fruits and vegetables. This increases the risk of deficiencies in essential micronutrients such as magnesium, B vitamins, vitamins A, E, C, and D, which could negatively impact both maternal health and fetal development [60].

The limited available data involves two case studies of women who followed the ketogenic diet during pregnancy [56].

• 1.Case 1: A 27-year-old woman followed a ketogenic diet during her first pregnancy due to a history of a brain tumor that had caused seizures. She observed that high carbohydrate intake triggered frequent seizures, which decreased as she reduced carbohydrates. During her pregnancy, she adopted a classical ketogenic diet, reducing seizures to one or none daily. However, her micronutrient levels were disrupted, including low carnitine at 14 weeks, altered levels of vitamins A, D, and E, and elevated cholesterol and triglycerides. She gained 9 kg during pregnancy and delivered a healthy male infant with a normal APGAR score, normal serum glucose levels, and no urinary ketones within the first 24 h. The child exhibited normal growth and development, while the mother continued the diet during lactation.
• 2.Case 2: A 36-year-old woman who had experienced seizures since she was 14 years old reduced them to zero by limiting carbohydrate intake to 20 g/day. During pregnancy, her carbohydrate intake was increased to 30 g/day, and she took supplements including folic acid, calcium, vitamin D, and prenatal vitamins. Seizures occurred 1–4 times a month, and her pregnancy weight gain was 5.9 kg. She delivered a healthy male infant at 40 + 2 weeks with a normal APGAR score. The infant exhibited minor ear abnormalities but normal hearing and metabolic function. At 6 months, the infant's development was normal.

The ketogenic diet induces a state of ketosis, where the body shifts from using glucose as its primary energy source to metabolizing fatty acids into ketone bodies. While this adaptation may be beneficial in managing conditions like epilepsy or insulin resistance, the biochemical implications during pregnancy require careful consideration. Glucose is the preferred energy source for the developing fetus, particularly for brain development. Prolonged reliance on ketone bodies could theoretically impact fetal neurodevelopment, as ketones may alter pathways for cell growth and differentiation. Additionally, the restrictive macronutrient composition of the ketogenic diet increases the risk of deficiencies in vital nutrients like folic acid, magnesium, and vitamins A and D, which are crucial for proper organogenesis and maternal health. The metabolic changes induced by ketosis could also stress maternal homeostasis, potentially exacerbating conditions like gestational diabetes or preeclampsia in vulnerable populations. Moreover, the broader implications of the ketogenic diet during pregnancy extend to its potential to affect placental function and fetal growth. Ketone bodies can cross the placenta, influencing fetal metabolism and potentially causing long-term metabolic reprogramming [61].

5.3. Gluten-free diet

The gluten-free diet excludes gluten, a protein found in wheat, barley, and rye. It is specifically designed for celiac disease patients, serving as the only effective treatment to date [62]. It is also recommended for other gluten-related disorders, such as wheat allergies.

This diet includes meat and its products, dairy products, vegetables, and fruits, while permitted grains include rice, corn, and pseudocereals like amaranth and quinoa [59]. Prohibited foods include wheat, barley, rye, oats, and their derivatives like flour, bread, pasta, and cakes [63].

Adopting a gluten-free diet poses challenges, including reduced taste, accessibility, and higher cost. Moreover, gluten-containing foods often provide essential nutrients, making nutrient imbalances a risk. Specifically, deficiencies in iron, calcium, magnesium, fiber, folic acid, vitamin D, and zinc are possible [62].

Foods rich in these nutrients and gluten-free alternatives include [62]:

Iron: Spinach, sweet potatoes, peas, broccoli, leafy greens, beef, lamb, eggs, nuts, and dried fruits.

Folic Acid: Lentils, leafy greens, peanuts, citrus fruits, and broccoli. Note that gluten-free products are rarely fortified with folic acid.

Calcium, Vitamin D, and Magnesium: Fortified beverages, dairy products, canned fish, leafy greens, broccoli, nuts, beans, and sesame seeds.

Omega-3 Fatty Acids: Tuna, salmon, sardines, and trout.

Fiber: Brown rice, corn, amaranth, gluten-free oats, millet, quinoa, chard, potatoes, beans, nuts, and dried apricots.

Women with celiac disease face a higher risk of preterm birth, restricted intrauterine growth, stillbirth, and low birth weight [64,65]. While the mechanisms remain unclear, malnutrition and the autoimmune nature of the disease are the leading hypotheses [66]. Pregnant women with untreated celiac disease are six times more likely to miscarry, but following a strict gluten-free diet reduces this risk ninefold [67,68]. Additionally, gluten avoidance may reduce the risk of certain congenital abnormalities in the heart and urinary system [69]. Thus, for women with celiac disease, adhering to a gluten-free diet is essential for a healthy pregnancy outcome.

For women without celiac disease or related conditions, there is no evidence to suggest that avoiding gluten provides any benefits to them or their fetuses [70]. In contrast, gluten-free diets have been associated with higher rates of hypothyroidism, irritable bowel syndrome, fewer pregnancies and live births, and lower body mass index at delivery [71]. Furthermore, the exclusion of gluten-rich foods poses the risk of nutrient deficiencies without being strictly necessary.

5.4. Mediterranean Eating Pattern-PMC

The Mediterranean Eating Pattern has gained widespread recognition as a healthy dietary pattern, known for reducing the risk of heart disease, certain cancers, diabetes, metabolic syndrome, and depression.

Its principles include: a) Daily, abundant consumption of vegetables, fruits, legumes, and nuts; b) A substantial intake of whole grains, such as whole-grain bread and brown rice; c) Extra virgin olive oil as the primary source of healthy fats; d) Weekly consumption of fish, particularly those rich in omega-3 fatty acids; e) Moderate intake of yogurt and cheese; f) Limited or no consumption of red meat, favoring poultry, fish; g) minimal intake of sweets, sugar-sweetened beverages, and butter and h) moderate consumption of wine with meals, excluding this step during pregnancy and lactation.

5.4.1. Foods included in the mediterranean diet

The Mediterranean diet, rooted in the culinary traditions of the Mediterranean region, emphasizes locally produced foods such as fruits, vegetables, whole grains, legumes, nuts, and seeds. It incorporates moderate amounts of fish, poultry, dairy, and red wine, with minimal red meat, and highlights olive oil as the primary fat source [72,73].

In summary, the advantages of the Mediterranean diet are: a) reduction of saturated and trans fats; b) inclusion of healthy unsaturated fats, particularly omega-3 fatty acids; c) limitation of sodium intake, restriction of processed carbohydrates and preference for foods rich in fiber and antioxidants [74].

Table 1 summarizes the portion of foods on the Mediterranean Eating Pattern.

Table 1.

Portion of foods in the mediterranean eating pattern.

Food	Quantity	Serving Size
Fresh Fruits and Vegetables	Fruits:3 servings/day Vegetables: at least 3 servings/day	Fruits:1/2-1 Cup Vegetables:1/2 cup cooked or 1 cup raw
Whole Grains and Starchy Vegetables	3-6 servings/day	½ cup cooked grains, pasta or cereal 1 slice bread 30g cup dry cereal
Extra Virgin Olive Oil	1-4 servings/day	1 tablespoon
Legumes	3 servings/week	½ cup
Fish	3 servings/week	100 g
Nuts	At least 3 servings/week	¼ cup or 2 tablespoons nut butter
Poultry	No more than once a day (less is better)	85 g
Dairy	No more than once a day (less is better)	1 cup milk or yogurt 40 g natural cheese
Eggs	Up to 1 yolk/day	1 egg
Red Meat	None or no more that 1 serving/week	85 g
Wine	1 serving/day (it is not recommended during pregnancy and lactation)	1 glass (it is not recommended during pregnancy and lactation)
Sweets	Avoid processed sweets, limit homemade sweets to 3 servings/week	Varies by type of sweet

It is important to note that with appropriate modifications, the Mediterranean diet can be adapted as a vegetarian or gluten-free diet.

The influence of the Mediterranean Diet during pregnancy and the perinatal period has been extensively studied over the years. This dietary pattern is not only sufficient for a healthy pregnancy but is also accompanied by numerous benefits for both the mother and the developing fetus. Specifically, recent studies report a protective effect against asthma and atopy in children, reducing the tendency for allergies [[75], [76], [77]]. A noteworthy finding is the reduced risk of gestational diabetes, with rates of reduction reaching up to 65 % [[77], [78], [79]]. Additionally, it improves outcomes such as preterm birth rates [[76], [77], [78]], pregnancy-induced hypertension, and preeclampsia [77,78]. Due to improved blood flow to the placenta, the risks of low birth weight [[76], [77], [78]] and intrauterine growth restriction [78] are also decreased. There is also a reduction in the rates of emergency cesarean sections and perineal trauma, which may be attributed to the generally improved course of pregnancy and the lower frequency of macrosomia due to better glucose regulation [77].

This diet also appears to provide protection against cardiometabolic risks [76,77], heart anomalies of the septum and atrial chamber, reduced systolic and diastolic blood pressure, prevention of vascular obstruction, and gastroschisis [77]. Finally, it reduces the risk of spina bifida due to higher plasma folate and vitamin B12 levels and lower serum homocysteine in the mother [79]. Fewer instances of urinary tract infections during pregnancy have also been reported [77], thanks to the Mediterranean Diet's ability to lower inflammatory markers and modulate immunity.

5.5. Diabetic diet

In recent years, the prevalence of diabetes has steadily increased, and pregnancy is no exception. In the United States, the incidence of diabetes during pregnancy rose from 6 % in 2016 to 8.3 % in 2021, including women with type 1, type 2, and gestational diabetes [80].

These individuals require a specialized dietary plan to maintain normal blood sugar levels, achieve a healthy weight, and avoid risks associated with diabetes. The goal is to keep blood sugar levels within acceptable limits through diet, preventing hyperglycemia, which, if persistent, may cause damage to nerves, kidneys, and the heart [81]. For individuals with type 2 diabetes, proper nutrition also aids in weight loss, which further improves blood sugar regulation [82]. It is recommended to consume three main meals and a few snacks in between, without skipping any, as periodic meal consumption helps the body use insulin more effectively, whether it is naturally produced or administered as medication.

Ideally, similar quantities of food should be consumed at approximately the same time daily to prevent episodes of hyperglycemia or hypoglycemia (NHS, 2024) [83].

5.5.1. Carbohydrates

Carbohydrates cause a rapid rise in blood sugar levels, so it is advised to consume them in combination with fats, fiber, and proteins to slow digestion and allow carbohydrates to enter the bloodstream more gradually [84].

Carbohydrates include sugars, also known as simple carbohydrates, and starches, which are complex carbohydrates. Complex carbohydrates have a low glycemic index and are more suitable for a diabetic diet. Healthy choices include: fruits, vegetables, whole grains, legumes, such as beans and low-fat dairy products, like milk and cheese [85].

Conversely, foods or drinks high in simple carbohydrates should be avoided, such as: fruit juices (especially the processed), honey, sugar, sweets, alcohol sugary sodas and foods and beverages with added sugars, such as cereals and chocolate drinks [86].

5.5.2. Fiber

Dietary fiber plays a key role in how the body digests food and helps balance blood sugar levels. Foods rich in fiber include vegetables, fruits (for maximum fiber intake, consume whole fruits instead of their juices), nuts, legumes, whole grains, fish rich in omega-3s but low in mercury [87].

5.5.3. Fats

Foods containing monounsaturated and polyunsaturated fats are recommended, as they help lower cholesterol levels. However, they should be consumed in moderation due to their high caloric content, which could cause excessive calorie intake. Examples include avocado, nuts and olive oil [83].

5.6. Intermittent fasting

While most diets focus on ∗what∗ to eat, the main principle of intermittent fasting is ∗when∗ to eat.

There are various approaches to this diet. The most popular is the 16/8 fasting method, which involves eating during an 8-h window and abstaining from food for the remaining 16 h of the day. Another pattern is the 5:2 method, where one eats normally for five days a week and restricts intake on the remaining two days. Lastly, alternate-day fasting involves eating normally one day and either fasting completely or consuming very few calories (e.g., 500) the next day [88].

During fasting periods, only water and unsweetened beverages, like coffee and tea, are allowed. During eating periods, it is important not to overeat, especially high-calorie or low-nutrient foods, as this negates the benefits of fasting [89].

The benefits of this dietary pattern are not limited to fat burning. According to Mattson, "Many things happen during intermittent fasting that can protect organs from chronic diseases such as type 2 diabetes, heart disease, age-related neurodegenerative disorders, inflammatory bowel disease, and even some cancers" [90].

Summarizing data from various studies, this pattern shows benefits for cognitive function and memory, physical performance, type 2 diabetes, obesity, and tissue health [89].

Intermittent fasting, particularly time-restricted feeding (TRF), has demonstrated significant benefits in improving metabolic and reproductive health, particularly in women with polycystic ovary syndrome (PCOS). Studies reveal that TRF effectively reduces hyperandrogenism, marked by decreased levels of testosterone and the free androgen index (FAI), while increasing sex hormone-binding globulin (SHBG). These hormonal adjustments contribute to improved menstrual regularity and fertility. Furthermore, TRF aligns feeding schedules with circadian rhythms, optimizing endocrine function and enhancing insulin sensitivity—key factors in addressing metabolic disturbances. These benefits suggest potential applications of IF in improving reproductive outcomes; however, limited research exists specifically addressing pregnant populations [91].

During pregnancy, a cautious approach toward intermittent fasting is warranted. A recent review of 18 studies focusing on women fasting during Ramadan reported some evidence that prolonged fasting could negatively impact birth weight [92]. Additionally, the same review suggested associations with reduced amniotic fluid levels and an increased risk of preterm birth. Another review from 2023 identified further potential adverse effects, such as a low Biophysical Profile score [93].

On the other hand, intermittent fasting has shown promising effects on blood sugar regulation. Long-term studies have demonstrated that consuming food within a restricted 8-h window improves insulin sensitivity, beta-cell responsiveness, fasting glucose levels, and fasting insulin levels [94,95]. These findings suggest that such a dietary pattern could be adapted for individuals with glucose metabolism issues, including gestational diabetes mellitus (GDM). For instance, one study found that each 1-h extension of the fasting window was associated with a 0.03 mmol/L decrease in fasting glucose concentrations [96].

Several studies have also investigated the effects of fasting interventions on health outcomes in individuals, particularly those with PCOS or in pre- and post-menopausal stages. A study conducted during Ramadan (April–May 2022) [97] assessed the impact of Ramadan Intermittent Fasting and reported significant improvements in body composition, lipid profiles, and inflammatory markers, especially in pre-menopausal women. The study observed notable reductions in body fat, waist circumference, triglyceride levels, and pro-inflammatory markers such as tumor necrosis factor-α (TNF-α) and C-reactive protein, along with increases in high-density lipoprotein cholesterol (HDL-C) levels and antioxidant activity. Furthermore, post-menopausal women experienced significant reductions in diastolic blood pressure, suggesting that Ramadan Intermittent Fasting could enhance cardiometabolic and oxidative health. However, the transient nature of these improvements highlights the need for sustainable post-Ramadan strategies to maintain the observed benefits.

Insights from Ramadan fasting studies provide valuable real-world perspectives on prolonged fasting during pregnancy. While improvements in glucose metabolism have been observed, concerns regarding potential risks such as low birth weight and reduced amniotic fluid levels highlight the necessity for caution. Existing evidence underscores the importance of individualized dietary guidance, emphasizing close monitoring and adaptation of fasting protocols to prioritize maternal and fetal health. The limited scope of current studies, primarily short-term interventions in non-pregnant populations, highlights the urgent need for larger, long-term trials to establish the safety and efficacy of IF during pregnancy [91].

Another study [98], examined Early Time-Restricted Eating in women with PCOS, either alone or with probiotics, and found no significant advantages over a standard daily calorie restriction diet. All interventions resulted in similar improvements in body weight, BMI, vascular risk indicators, and hirsutism, with no substantial effects on insulin resistance, lipid profiles, or hormonal levels, indicating that weight loss, rather than diet type, was the main contributor to these improvements. A third study [99], assessed the impact of an 8-h TRF diet on women with PCOS over six weeks, revealing significant reductions in BMI, waist-to-hip ratio, insulin resistance, and fasting insulin and glucose levels. It also improved lipid profiles, reduced levels of AMH, testosterone, and other androgens, and increased SHBG, while lowering fecal calprotectin, suggesting improvements in gut health. These findings point to the potential benefits of TRF in alleviating PCOS symptoms such as hyperandrogenism and metabolic risks. However, all studies faced limitations, including small sample sizes, short durations, and lack of control groups, highlighting the need for further research to determine long-term effects, assess inflammation markers, and identify the optimal duration for these dietary interventions.

Studies suggest that fasting can reduce androgen levels (such as testosterone and free androgen index) and increase sex hormone-binding globulin, which may help alleviate hyperandrogenic symptoms like hirsutism and acne, especially when food is consumed earlier in the day. For example, early time-restricted eating and the 5:2 diet have been associated with significant decreases in androgens and improvements in sex hormone-binding globulin. However, fasting does not appear to impact other reproductive hormones such as estradiol, gonadotropins (LH and FSH), or prolactin. These effects are primarily observed with weight loss and may be more pronounced when meals are consumed earlier in the day, suggesting that early eating may be more beneficial for regulating androgen levels in women with PCOS. Further research is needed to confirm these findings and determine optimal fasting protocols for improving reproductive health in women [100].

Overall, this dietary pattern may be followed during pregnancy in certain cases, depending on the fasting protocol. Women who wish to include periods of fasting should listen to their bodies and break the fast if they feel the need for food, drink plenty of water, rest, ensure they do not lose weight, and be monitored more closely by their doctor or midwife during the fasting periods.

Table 2 provides a comparative overview of the benefits and risks associated with various dietary patterns during pregnancy, based on current research.

Table 2.

Comparative overview of the benefits and risks associated with various dietary patterns during pregnancy, based on current research.

Dietary Pattern	Benefits	Risks/Challenges
Mediterranean Diet	-Reduces risk of gestational diabetes, preterm birth, and low birth weight -Improves placental blood flow and fetal growth -High in antioxidants and healthy fats	-May require guidance for proper adaptation to non-Mediterranean cuisines -Moderate cost of specific foods (e.g., olive oil, fresh fish)
Vegetarian Diet	-Can meet nutritional needs if well-planned -Lower risk of preeclampsia and gestational diabetes -Nutrient-rich in fiber and plant-based foods	-Risk of deficiencies in vitamin B12, iron, omega-3 fatty acids, and calcium without careful planning
Vegan Diet	-High in plant-based nutrients and fiber -Reduces risk of certain chronic diseases if balanced	-Higher risk of deficiencies (vitamin B12, omega-3, calcium, iron) -Requires supplements and strict planning
Ketogenic Diet	-May help with seizure management (limited data)	-Insufficient evidence on safety during pregnancy -Risk of micronutrient deficiencies (e.g., magnesium, B vitamins)
Gluten-Free Diet	-Essential for women with celiac disease or gluten intolerance -Reduces risks of miscarriage and preterm birth in these populations	-Nutritional deficiencies in iron, fiber, folic acid, and vitamin D without careful planning -Higher cost and limited food variety
Diabetic Diet	-Helps manage blood sugar levels -Reduces pregnancy complications associated with diabetes -Focuses on low glycemic index foods and balanced meals	-Requires consistent meal timing and monitoring to prevent hypoglycemia or hyperglycemia
Intermittent Fasting	-May help regulate glucose levels (limited evidence)	-Potential risk of low birth weight and reduced amniotic fluid -Not recommended without medical supervision

6. Implications for future research

Future research should focus on the long-term safety and efficacy of less-studied dietary patterns during pregnancy and lactation, with particular emphasis on the ketogenic diet and intermittent fasting. Although the ketogenic diet has shown promise in managing specific conditions such as epilepsy, its strict macronutrient restrictions raise concerns about potential micronutrient deficiencies and its impact on fetal development. Rigorous longitudinal studies are needed to evaluate its effects on maternal and fetal health outcomes comprehensively.

Similarly, intermittent fasting requires further investigation to elucidate its influence on glucose regulation, birth weight, and the risk of gestational complications. Vegetarian and vegan diets, while generally considered safe when appropriately planned, would benefit from additional research to establish precise supplementation protocols and ensure adequate intake of critical nutrients such as vitamin B12, iron, and omega-3 fatty acids.

Lastly, while the Mediterranean diet has demonstrated significant protective benefits, further studies should explore its impact across diverse populations and examine ways to adapt its principles to various cultural dietary practices. These research efforts are crucial for developing evidence-based nutritional recommendations to support the health and well-being of pregnant and lactating individuals.

While this review provides a comprehensive analysis of popular dietary patterns such as the Mediterranean, vegetarian/vegan, and gluten-free diets, it predominantly focuses on Western dietary practices. This emphasis limits the applicability of findings to non-Western contexts, where dietary habits, staple foods, and nutritional challenges differ significantly. For instance, diets in South Asia, East Asia, and Sub-Saharan Africa often rely heavily on rice, millet, or other indigenous grains and include unique traditional practices that influence nutrient intake [101]. Future research should explore how these dietary patterns can be adapted to suit non-Western populations, ensuring that nutritional guidance accounts for cultural preferences, accessibility of foods, and socio-economic constraints. Addressing these factors would enhance the global relevance and practical application of the findings presented in this review.

7. Conclusions

Each dietary pattern presents unique advantages, limitations, and challenges. Provided the selected foods adequately support the physiological demands of pregnancy, promote fetal development, and ensure sufficient nutrient intake during lactation, mothers should not be discouraged from adopting these patterns. Healthcare professionals involved in maternal care must be well-prepared to guide individuals through this nutritionally complex period. They should offer specialized and evidence-based advice regarding the clinical adequacy of a given diet, emphasizing which foods to prioritize and identifying those that should be limited or avoided entirely. Particular attention is warranted in cases where dietary patterns are dictated by medical conditions such as diabetes or celiac disease. In such scenarios, appropriate dietary modifications are essential, as adherence to these specialized diets is imperative to prevent complications during pregnancy.

CRediT authorship contribution statement

Maria Chouli: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Anastasia Bothou: Writing – review & editing, Visualization, Resources, Methodology, Investigation. Giannoula Kyrkou: Writing – review & editing, Resources, Methodology. Sofia Kaliarnta: Writing – review & editing, Resources, Methodology. Aikaterini Dimitrakopoulou: Writing – review & editing. Athina Diamanti: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization.

Fundings

This review did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Conflict of interest

The authors declare no competing interests.