Researchers studied whether two important vitamins—folate and B12—affect how well the placenta grows during the first three months of pregnancy. The placenta is the organ that feeds and protects a developing baby. Scientists looked at pregnant women’s vitamin levels and measured their babies’ placental growth. This research matters because folate and B12 help build new cells, which is especially important when a baby is developing. Previous studies show that getting enough of these vitamins can prevent birth defects and reduce pregnancy complications. This new study helps doctors understand exactly how these vitamins support healthy pregnancy from the very beginning.

The Quick Take

  • What they studied: Whether the amount of folate and vitamin B12 in a pregnant woman’s blood during the first three months affects how well her baby’s placenta grows
  • Who participated: Pregnant women enrolled in the Rotterdam Periconception Cohort study who had their vitamin levels measured in early pregnancy and had ultrasound measurements of placental growth
  • Key finding: The study suggests that folate and B12 levels in early pregnancy may be connected to placental growth, which is important for healthy fetal development
  • What it means for you: If you’re planning to get pregnant or are newly pregnant, maintaining adequate folate and B12 levels appears important for supporting your baby’s early development. Talk to your doctor about whether you need supplements, especially if you follow a vegetarian or vegan diet (B12 sources are limited in plant foods)

The Research Details

This was a cohort study, which means researchers followed a group of pregnant women over time and measured specific things about them. The scientists collected blood samples from women during their first trimester (the first three months of pregnancy) and measured how much folate and vitamin B12 they had. They also used ultrasound—the same imaging tool used to see babies during pregnancy—to measure how large the placenta was growing. By comparing the vitamin levels to the placental measurements, they could see if there was a connection between the two.

This type of study is useful because it follows real pregnancies as they happen, rather than just looking at past records. The researchers could measure vitamins at the exact time they wanted (early pregnancy) and then track what happened with placental growth.

The placenta is like a lifeline between mother and baby—it brings oxygen and nutrients to the developing baby and removes waste. If the placenta doesn’t grow properly, the baby might not get enough nutrition, which could cause problems. Folate and B12 are essential for making new cells, which is exactly what happens during placental and fetal development. Understanding this connection helps doctors know which vitamins are most important to monitor during early pregnancy.

This study was published in a peer-reviewed medical journal, meaning other experts reviewed the research before it was published. The study is based on the Rotterdam Periconception Cohort, which is a well-established research group that has produced reliable findings. However, readers should know that the sample size wasn’t specified in the available information, which makes it harder to judge how confident we should be in the results. The study measures associations (connections) rather than proving cause-and-effect, so we can’t say that low vitamins definitely cause poor placental growth—only that they appear related.

What the Results Show

The research suggests that folate and vitamin B12 levels during the first trimester are associated with how well the placenta grows. This means women with adequate levels of these vitamins tended to have better placental growth compared to those with lower levels. The connection makes biological sense because both folate and B12 are needed for a process called “one-carbon metabolism,” which is essentially the body’s way of building new cells and DNA—the instructions for life. During early pregnancy, this process is working overtime to create the placenta and the baby’s tissues.

The study adds to existing evidence showing that these vitamins matter for pregnancy health. Previous research has already shown that folic acid supplements (a form of folate) can prevent neural tube defects—serious birth defects affecting the brain and spine. This new research suggests the benefits may extend to supporting overall placental development, which is foundational for the entire pregnancy.

Beyond placental growth, the research connects to broader pregnancy health. Studies mentioned in the background show that deficiencies in folate and B12 have been linked to serious pregnancy complications including preeclampsia (dangerously high blood pressure during pregnancy) and low birth weight (babies born smaller than healthy). While this particular study focused on placental growth as the main outcome, the findings support the idea that maintaining good vitamin status early in pregnancy may help prevent these complications.

This research builds on decades of evidence about folate’s importance in pregnancy. The connection between folic acid supplementation and prevention of neural tube defects is well-established and is why doctors recommend prenatal vitamins containing folic acid. However, less research has focused specifically on how these vitamins affect placental growth in the first trimester. This study fills that gap by showing the mechanism might involve supporting the placenta’s development from the earliest stages. The findings align with what we know about how these vitamins work at the cellular level.

The study measures associations rather than proving cause-and-effect, so we can’t say with certainty that low vitamins cause poor placental growth—only that they appear connected. The sample size wasn’t clearly reported, which affects how confident we can be in the results. Additionally, this study looked at one specific population (the Rotterdam cohort), so results might not apply equally to all pregnant women worldwide. The research also doesn’t tell us the exact vitamin levels that are ‘ideal’—just that higher levels were associated with better outcomes. Finally, the study was observational, meaning researchers watched what happened naturally rather than randomly assigning some women to take supplements and others not to, which would provide stronger evidence.

The Bottom Line

If you’re pregnant or planning pregnancy, ensure you’re getting adequate folate and B12. For folate: Take a prenatal vitamin containing at least 400 micrograms of folic acid daily, starting before conception if possible. For B12: If you eat animal products (meat, dairy, eggs), you likely get enough from food. If you’re vegetarian or vegan, ask your doctor about B12 supplements or fortified foods. These recommendations have moderate to strong evidence supporting them. Discuss your specific needs with your healthcare provider, especially if you have dietary restrictions or a history of pregnancy complications.

Anyone planning to become pregnant should pay attention to this research. Women already pregnant, especially in the first trimester, should ensure adequate vitamin intake. This is particularly important for vegetarians and vegans (who may lack B12), women with certain digestive conditions that affect nutrient absorption, and those with a history of pregnancy complications. If you’re not planning pregnancy, this research is less immediately relevant to you, though folate and B12 are important for everyone’s health.

Vitamin levels matter most during the first trimester when the placenta is forming and the baby’s major organs are developing. If you’re planning pregnancy, start taking prenatal vitamins at least one month before trying to conceive. If you’re already pregnant, begin supplementation as soon as you know. You should see the benefits reflected in placental development during the first trimester ultrasounds (typically around 11-14 weeks). The full impact on pregnancy outcomes (preventing complications, supporting healthy birth weight) develops throughout pregnancy and becomes apparent at delivery.

Want to Apply This Research?

  • Log your daily prenatal vitamin intake and any B12 supplements. Track the specific amounts of folate and B12 if your prenatal vitamin lists them. If you have ultrasound measurements of placental size from your doctor, you can record these dates and measurements to monitor progress over time.
  • Set a daily reminder to take your prenatal vitamin at the same time each day (many people choose breakfast or bedtime). If you’re vegetarian or vegan, add a B12 supplement or fortified food to your daily routine. Use the app to log which foods you eat that contain folate (leafy greens, legumes, asparagus) and B12 (fortified cereals, nutritional yeast, supplements) to ensure variety in your diet.
  • Create a monthly check-in to review your supplement adherence. If you have prenatal appointments with ultrasounds, record the dates and any measurements your doctor provides. Use the app to track any pregnancy symptoms or concerns to discuss with your healthcare provider. Set a reminder to discuss your vitamin levels with your doctor at each prenatal visit, especially if you have dietary restrictions or absorption concerns.

This research summary is for educational purposes only and should not replace medical advice from your healthcare provider. The study shows associations between vitamin levels and placental growth but does not prove cause-and-effect. Pregnancy is highly individual, and vitamin needs vary based on your diet, health conditions, and medical history. Always consult with your obstetrician, midwife, or primary care doctor before starting, stopping, or changing any supplements during pregnancy. If you have concerns about your vitamin levels or pregnancy health, seek professional medical evaluation. This summary is based on research published in 2025 and reflects current scientific understanding, but medical recommendations may evolve as new evidence emerges.