Prenatal vitamins and folic acid
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Importance of Prenatal Vitamins and Folic Acid in Pregnancy
Prenatal vitamins are essential during pregnancy because they provide increased amounts of key nutrients that are difficult to obtain from diet alone. Among these, folic acid is especially important for both maternal and fetal health. Deficiency in folic acid can lead to anemia and nerve problems in the mother, and serious birth defects such as neural tube defects (NTDs) in the baby. Supplementing with folic acid around conception and during early pregnancy is proven to reduce the risk of NTDs, preterm birth, and congenital heart disease 15.
Recommended Dosage and Timing of Folic Acid Supplementation
Health authorities, including the World Health Organization and national guidelines in countries like Canada, recommend that women planning pregnancy and those who are pregnant take a daily supplement containing 400 micrograms (µg) of folic acid, starting before conception and continuing through pregnancy and lactation 35. However, many prenatal supplements on the market contain higher doses, often 800–1000 µg or more, which exceeds the recommended amount. This has led to concerns about unnecessarily high blood folate levels, the long-term effects of which are not fully understood 37.
Bioavailability and Forms of Folic Acid in Prenatal Supplements
Most prenatal vitamins contain synthetic folic acid, but some now include l-methylfolate, the bioactive form of folate. About 40–60% of people have genetic differences (MTHFR polymorphisms) that make it harder to convert folic acid into its active form. For these individuals, l-methylfolate may be a better option, as it is more readily used by the body and can help prevent folate deficiency and related complications 15. Studies show that both folic acid and l-methylfolate increase blood folate levels and reduce homocysteine, a risk factor for pregnancy complications 15.
Health Outcomes Linked to Prenatal Folic Acid Supplementation
Neural Tube Defects and Other Birth Defects
Consistent evidence shows that taking folic acid before and during early pregnancy significantly reduces the risk of neural tube defects in babies 135.
Autism Spectrum Disorder (ASD)
Some studies suggest that prenatal vitamin or folic acid use in the first month of pregnancy may lower the risk of autism spectrum disorder in children, although results are not always statistically significant and more research is needed 28.
Childhood Leukemia
Large studies indicate that maternal use of folic acid and other vitamins before and during pregnancy is associated with a reduced risk of childhood acute lymphoblastic leukemia (ALL) and possibly acute myeloid leukemia (AML) .
Obesity in Children Born Small for Gestational Age (SGA)
Prenatal folic acid supplementation, especially when combined with multivitamins or iron, may lower the risk of obesity in preschool girls born SGA, but this effect was not seen in boys .
Challenges and Considerations in Folic Acid Supplementation
Despite clear recommendations, many women do not take folic acid at the right time or in the recommended dose. Only a small percentage use supplements as advised, and factors such as young age, smoking, low socioeconomic status, and ethnicity can increase the risk of folate deficiency . There is also confusion due to varying supplement formulations and unclear labeling, making it difficult for women and healthcare providers to choose the right product 37.
Conclusion
Prenatal vitamins, especially those containing folic acid, are crucial for preventing birth defects and supporting healthy pregnancy outcomes. The recommended dose is 400 µg daily, starting before conception. While most supplements provide more than this amount, there is no clear evidence that higher doses offer additional benefits for most women. The use of l-methylfolate may be preferable for women with certain genetic backgrounds. Ensuring that all women of childbearing age have access to the right information and supplements is key to improving maternal and child health 1359.
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