A 2026 study of 230 pregnant women found that those following a vegan diet consumed significantly less protein (60 grams daily versus 82 grams) and had higher rates of babies born smaller than expected. According to Gram Research analysis, babies whose mothers had higher protein intake and adequate leucine, a key amino acid, weighed on average 267 grams more at birth. Vegan mothers also had lower intakes of vitamin B12, vitamin D, calcium, and DHA, nutrients that require careful planning or supplementation in plant-based pregnancy diets.
A new study of 230 pregnant women found that those following a vegan diet had lower protein intake and higher rates of babies born smaller than expected. According to Gram Research analysis, vegan mothers consumed about 60 grams of protein daily compared to 82 grams for non-vegan mothers. The research shows that getting enough protein, especially certain amino acids like leucine, may help babies grow to a healthier birth weight. While vegan diets provided more fiber, folate, and iron, they fell short in vitamin B12, vitamin D, calcium, and other nutrients important for pregnancy.
Key Statistics
A 2026 study of 230 pregnant women found that vegan mothers consumed 60 grams of protein daily compared to 82 grams for non-vegan mothers, a difference of 22 grams per day.
Babies born to mothers with leucine levels above 5.636 percent of total protein weighed on average 267 grams (9.4 ounces) more at birth than babies whose mothers had lower leucine levels, according to a 2026 analysis of 230 pregnancies.
Vegan pregnant women had vitamin B12 intake of only 1.5 micrograms daily versus 4.6 micrograms for non-vegan mothers, and vitamin D intake of 0.24 micrograms versus 5.5 micrograms, a 2026 study of 230 women found.
A 2026 study of 54 vegan pregnant women found they had a higher rate of babies born smaller than expected for their age, with protein intake and amino acid composition identified as key factors affecting birth weight.
The Quick Take
- What they studied: Whether pregnant women eating a vegan diet get enough nutrients and how their diet affects their baby’s birth weight and growth
- Who participated: 230 pregnant women at a single medical center, including 54 who followed a strict vegan diet and 176 who ate non-vegan diets. All women had single pregnancies and delivered at the same hospital.
- Key finding: Vegan mothers had significantly lower protein intake (60 grams per day versus 82 grams), and babies born to vegan mothers were more likely to be smaller than expected for their age. Babies whose mothers got higher amounts of protein had lower risk of being born too small.
- What it means for you: If you’re pregnant and vegan, paying close attention to protein intake and specific amino acids may help your baby grow to a healthier birth weight. You should also consider supplements for vitamin B12, vitamin D, calcium, and other nutrients that are harder to get from plant-based foods. Talk with your doctor or a nutrition specialist about your specific needs.
The Research Details
Researchers looked back at information from pregnant women who had already given birth at one hospital. They divided the women into two groups: those who ate a vegan diet (no animal products at all) and those who ate regular diets. During the third trimester of pregnancy, about three months before delivery, the women filled out a detailed food questionnaire that asked what they ate and drank. The researchers then compared what the two groups ate and looked at whether differences in their diets connected to how much their babies weighed at birth.
The study measured specific nutrients like protein, amino acids (the building blocks of protein), vitamins, minerals, and fats. They used several statistical methods to find patterns, including looking at which nutrients were most important for predicting birth weight. They also checked hospital records to see which babies were born smaller than normal for their age.
This approach matters because it captures what pregnant women actually eat during the most important time for baby growth. By comparing vegan and non-vegan diets side by side, researchers could identify specific nutrients that might be missing from plant-based pregnancy diets. The study used real-world data from actual pregnancies and birth outcomes, making the findings more relevant to pregnant women than lab studies alone.
This study has some strengths and some limitations. The strength is that it looked at actual pregnancies and real birth outcomes rather than just measuring nutrients in a lab. The researchers used a validated food questionnaire, meaning the tool they used to measure diet has been tested and proven reliable. However, the study only included women from one hospital, so the results might not apply to all pregnant women everywhere. The study was observational, meaning researchers watched what happened rather than randomly assigning women to different diets, so we cannot be completely certain that lower protein caused smaller babies. There could be other differences between vegan and non-vegan mothers that affected the results.
What the Results Show
Vegan mothers ate significantly less protein than non-vegan mothers: 60 grams per day compared to 82 grams per day. When researchers looked at protein relative to body weight, the difference was even clearer: vegan mothers got 1.10 grams of protein per kilogram of body weight daily, while non-vegan mothers got 1.44 grams. Babies born to mothers with higher protein intake had lower risk of being born smaller than expected. Specifically, for every 1 percent increase in protein as part of total calories, the risk of a baby being born too small decreased by 20 percent.
One particular amino acid called leucine stood out as especially important. Babies whose mothers had leucine levels above 5.636 percent of their total protein weighed on average 267 grams more at birth (about 9.4 ounces) compared to babies whose mothers had lower leucine levels. This is a meaningful difference in newborn weight. The study also found that other amino acids like tyrosine and valine showed similar patterns, suggesting that the quality and type of protein matters, not just the total amount.
Beyond protein, the study found major differences in other nutrients between vegan and non-vegan diets. Vegan mothers ate more carbohydrates (256 grams versus 217 grams daily), more fiber (48 grams versus 30 grams), more folate (627 micrograms versus 416 micrograms), and more iron (17 milligrams versus 12 milligrams). These are generally positive findings, as fiber and folate are important for pregnancy health. However, vegan mothers consumed much less vitamin B12 (1.5 micrograms versus 4.6 micrograms), vitamin D (0.24 micrograms versus 5.5 micrograms), calcium (764 milligrams versus 1053 milligrams), and a fat called DHA that is important for baby brain development (essentially zero versus 0.07 grams). Vegan mothers also got less choline (270 milligrams versus 394 milligrams), another nutrient important for fetal brain development.
This research adds important new information to a limited body of evidence about vegan pregnancy. Previous studies have raised concerns about whether vegan diets provide enough nutrients during pregnancy, but few have looked specifically at how nutrient intake connects to actual birth outcomes. This study confirms earlier findings that vegan diets tend to be lower in vitamin B12, vitamin D, calcium, and DHA. The new finding about protein and amino acids, particularly leucine, provides specific guidance that was not well-documented before. The higher rate of small-for-gestational-age babies in vegan mothers aligns with some previous research but contradicts other studies, suggesting that the relationship between vegan diets and birth weight may depend on how carefully mothers plan their nutrition.
The study only included women from one hospital, so results might not apply to all pregnant women or all communities. The study was observational, meaning researchers could not randomly assign women to vegan or non-vegan diets to test cause and effect. Other differences between vegan and non-vegan mothers, such as overall health, exercise, stress levels, or access to healthcare, could have affected birth weight rather than diet alone. The study measured diet only once during the third trimester, so it did not capture what women ate earlier in pregnancy when baby development is also critical. The study did not measure whether vegan mothers took supplements, which could have changed the actual nutrients they received. Finally, the study included only 54 vegan mothers, which is a relatively small number for drawing firm conclusions.
The Bottom Line
If you are pregnant and follow a vegan diet, work with your doctor or a registered dietitian to ensure you get enough protein, aiming for at least 1.4 grams per kilogram of your body weight daily. Include a variety of plant proteins like legumes, nuts, seeds, and whole grains to get different amino acids. Take supplements for vitamin B12, vitamin D, and consider supplements for calcium, DHA, and choline, as these are difficult to get from plant foods alone. These recommendations are based on moderate-quality evidence from this study and should be personalized to your individual needs. High confidence: pregnant vegan women should supplement vitamin B12. Moderate confidence: protein intake and amino acid balance may affect birth weight.
This research is most relevant to pregnant women who follow a vegan diet or are considering becoming pregnant while vegan. It is also important for healthcare providers who care for pregnant vegan women, including doctors, midwives, and dietitians. Partners and family members of pregnant vegan women should understand these nutritional considerations to provide support. Women who are not vegan do not need to change their diet based on this research, though the findings about protein and amino acids may have broader relevance. Women with previous pregnancies resulting in small babies should discuss these findings with their healthcare provider.
Nutritional changes during pregnancy work best when started as early as possible, ideally before pregnancy or in the first trimester. However, improvements in protein and nutrient intake during the second and third trimester can still benefit baby growth. If you start taking supplements now, you should expect to see improved nutrient levels within weeks, though the effect on birth weight develops over months as the baby grows. After birth, continuing good nutrition remains important if you plan to breastfeed.
Frequently Asked Questions
Can you have a healthy vegan pregnancy and have a normal-sized baby?
Yes, but it requires careful planning. This study shows vegan mothers had higher rates of smaller babies, but many vegan pregnancies result in healthy, normal-weight newborns. The key is ensuring adequate protein intake (at least 1.4 grams per kilogram of body weight daily) and supplementing nutrients like vitamin B12, vitamin D, and calcium that are harder to get from plants.
What specific nutrients do vegan pregnant women need to supplement?
Vitamin B12 is essential and should always be supplemented on a vegan diet. Vitamin D, calcium, DHA (omega-3 fat for brain development), and choline are also important to supplement or get from fortified foods. Work with your doctor to determine which supplements you need based on your individual diet and blood test results.
How much protein do pregnant vegan women actually need?
This study suggests at least 1.4 grams of protein per kilogram of body weight daily. For a 70-kilogram (154-pound) woman, that would be about 98 grams of protein daily. Include varied plant proteins like legumes, nuts, seeds, whole grains, and soy products to get all essential amino acids your baby needs.
Does being vegan during pregnancy definitely cause smaller babies?
Not necessarily. This study found an association between vegan diets and smaller babies, but the relationship is not automatic. Many vegan pregnancies result in normal-weight babies. The increased risk appears connected to lower protein intake and missing nutrients, which can be addressed through careful planning and supplementation.
What is leucine and why does it matter for pregnancy?
Leucine is an amino acid, a building block of protein that plays a special role in muscle and tissue growth. This study found that babies whose mothers had adequate leucine weighed significantly more at birth. Getting leucine from varied plant proteins like legumes, nuts, and seeds helps ensure your baby grows properly.
Want to Apply This Research?
- Log daily protein intake in grams and track whether you meet your target (1.4 grams per kilogram of body weight). Also track supplement use for vitamin B12, vitamin D, calcium, and DHA to ensure consistency.
- Add one new plant-based protein source to each meal this week, such as lentils at lunch, tofu in dinner, or hemp seeds on breakfast. Set a daily reminder to take prenatal supplements, especially B12 and vitamin D.
- Weekly review of protein intake and supplement adherence. Monthly check-ins with your healthcare provider to monitor weight gain, energy levels, and any pregnancy complications. Track any changes in how you feel and share this information with your doctor at prenatal visits.
This research provides important information for pregnant women following a vegan diet, but it should not replace personalized medical advice from your healthcare provider. If you are pregnant or planning to become pregnant and follow a vegan diet, discuss these findings with your doctor, midwife, or registered dietitian who can assess your individual nutritional needs and recommend appropriate supplements. Birth weight is influenced by many factors beyond diet, including genetics, overall health, and prenatal care. This study was observational and cannot prove that lower protein directly causes smaller babies. Always follow your healthcare provider’s recommendations for prenatal care and nutrition.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.