Folic Acid and Vitamin B12 Interplay in Pregnant women with Hypothyroidism: Its Effects on Thyroid Hormones and Placental DNA Methylation

Background: Adequate folate and vitamin B12 intake during pregnancy is essential to prevent longterm maternal and fetal outcomes. Emerging evidence suggests that excessive folic acid combined with vitamin B12 deficiency may lead to epigenetic modifications, potentially affecting newborn development and increasing the risk of chronic diseases. Materials and Methods : Women aged 21– 45 years attending antenatal clinics from the first trimester or upon pregnancy confirmation were enrolled. Serum levels of FT3, FT4, TSH, folic acid, and vitamin B12 were measured across all trimesters and at delivery, along with cord blood sampling. DNA methylation analysis of MTHFR and TCN2 genes was performed on 16 placental samples. Statistical analysis was conducted using SigmaPlot 13, including ANOVA, Pearson’s and Spearman’s correlation, and ROC curve analysis. Results: TSH levels were significantly elevated in subclinical and overt hypothyroid groups across all trimesters (p < 0.001). In cord blood, the folic acid/B12 ratio negatively correlated with FT3 and FT4 in control and subclinical hypothyroid (SCH) groups, and positively with TSH in the SCH group (p < 0.033). Methylation analysis revealed low CpG methylation in MTHFR and TCN2, methylation at promoter site in one sample. Conclusion: Balanced folic acid and B12 intake is critical in pregnancy. High folic acid with B12 deficiency may disrupt thyroid hormone levels and induce subtle epigenetic effects, recommending broader studies on global methylation and gene expression.