Neural tube abnormalities and Homocysteine and Thyroid Hormones: A Case-Control Investigation

Abstract

Background: Neural tube defects (NTDs) are severe congenital anomalies resulting from failure of neural tube closure during early embryogenesis and remain a major cause of fetal loss, infant mortality, and lifelong disability worldwide. Although periconceptional folic acid supplementation substantially reduces NTD risk, a considerable residual burden persists, suggesting the involvement of additional nutritional and metabolic factors.
Objective: To investigate the associations of maternal folate, vitamin B12, homocysteine, and thyroid hormones with fetal neural tube defects.
Methods: A hospital-based analytical case–control study was conducted at Salah Aldin General Hospital, Iraq, from October 2025 to may 2026. A total of 120 pregnant women with singleton pregnancies at 14–22 weeks of gestation were enrolled, including 60 cases with fetuses diagnosed with NTDs and 60 controls with structurally normal fetuses. Data on sociodemographic characteristics, obstetric history, and periconceptional folic acid supplementation were collected using structured interviews. Serum and red blood cell folate, vitamin B12, plasma homocysteine, and thyroid hormones (TSH and FT4) were measured using standardized immunoassays.
Results: : Regular periconceptional plasma homocysteine levels were significantly higher (14.9 ± 4.6 vs. 9.8 ± 3.1 µmol/L, p < 0.001). Thyroid dysfunction was also more common among cases, with higher mean TSH and lower FT4 levels (p ≤ 0.001). Combined folate and vitamin B12 deficiency was significantly associated with NTDs (p < 0.001). Multivariable analysis identified low serum folate (aOR = 3.94), low vitamin B12 (aOR = 3.12), elevated homocysteine (aOR = 4.58), high TSH (aOR = 2.63), and lack of folic acid supplementation (aOR = 3.71) as independent predictors of NTDs.
Conclusion: Maternal deficiencies of folate and vitamin B12, elevated homocysteine levels, and impaired thyroid function are significantly associated with increased risk of neural tube defects. These findings emphasize theimportance of integrated periconceptional nutritional and metabolic screening and intervention strategies, extending beyond folic acid supplementation alone, to further reduce the burden of NTDs.