Why Vitamin B12 Matters in Early Pregnancy: A New Study Reveals Long-Term Brain Benefits for Baby
If you’re newly pregnant — or planning to be — chances are you’ve started looking into all the right nutrients to support a healthy pregnancy. One vitamin that often flies under the radar? Vitamin B12. But new research is giving us even more reason to pay attention to this powerhouse nutrient, especially in early pregnancy.
A landmark 2024 study — the first triple-blind randomized controlled trial of its kind — has spotlighted vitamin B12’s critical role in your baby’s brain development, particularly during the first trimester. Researchers followed 249 mother-infant pairs, tracking B12 levels during pregnancy and assessing the children’s cognitive function at 4 years old. The findings are eye-opening.
B12 Deficiency Is More Common Than You Think
Despite an average B12 intake that was nearly double the recommended daily allowance, many of the pregnant women in the study were still deficient. In the first trimester, 26.1% had marginal B12 deficiency and 2.8% were outright deficient. By the third trimester, those numbers jumped significantly — nearly half of the women had marginal levels, and 15% were clinically deficient.
This tells us that B12 needs during pregnancy are higher than we once thought — and even a healthy-looking diet might not be enough.
Why the First Trimester Matters Most
The timing of B12 deficiency made a big difference. The study found that low B12 levels in the first trimester were linked to poorer cognitive outcomes in children at age 4. Specifically, researchers focused on working memory — a core function of the brain that supports problem-solving, attention, math, and language development. Children whose mothers had adequate B12 levels early in pregnancy performed significantly better in these areas.
That’s because neurogenesis — the process of forming new brain cells — is happening rapidly in the first few weeks of pregnancy, often before you even know you're pregnant.
How to Protect Your B12 Levels
The key takeaway? You need to think about B12 before pregnancy or as early as possible. Here’s what you can do:
Aim higher than the RDA. Most prenatal vitamins include some B12, but it may not be enough. Talk to your provider about your specific needs — especially if you follow a diet that’s low in animal products.
Test early. If you're planning a pregnancy or in the first trimester, ask your healthcare provider to check your B12 status. It's a simple blood test that can make a big difference.
Supplement if needed. Anyone avoiding meat, eggs, or dairy — including vegetarians, vegans, and some flexitarians — should strongly consider a high-quality B12 supplement. Methylcobalamin is a well-absorbed form commonly recommended in pregnancy.
The Bottom Line
This new study reinforces what nutrition experts have long suspected: vitamin B12 is essential for optimal brain development — and you can’t afford to wait until later in pregnancy to get enough of it. Starting preconception or in the first trimester gives your baby the best shot at healthy cognitive development.
For more on B12 and how to optimize your intake through real food and smart supplementation, check out Understanding Nutrients, where we dive deeper into nutrient needs for both mom and baby.
Your brain matters. So does your baby's. B12 is the link.