Maternal vitamin levels during pregnancies producing infants with neural tube defects.

Women at very high risk for having a child with a neural tube defect (NTD) because they had previously delivered affected children significantly reduced their recurrence rate by taking folate supplements before conception. To clarify how these results might apply to a lower-risk general obstetric population, we measured folate, vitamin B12, and retinol levels in maternal serum drawn early in 89 pregnancies resulting in NTD offspring and 178 control pregnancies identified from the Finnish Registry of Congenital Malformations. In 86.5% of the subjects, specimens were collected within 8 weeks after neural tube closure. In the NTD case mothers the mean (+/- SD) levels were not significantly lower than in control mothers: folate, 4.13 +/- 2.36 versus 4.28 +/- 2.52 ng/ml; vitamin B12, 482.8 +/- 161.1 versus 520.3 +/- 191.9 pg/ml; and retinol, 51.2 +/- 17.0 versus 50.5 +/- 16.9 micrograms/dl. After adjustment for age of the specimen, gestational age at which the specimen was drawn, maternal age, and maternal employment status, the odds ratios for being a case mother were 1.00 (95% confidence interval (CI) 0.91 to 1.10) for folate, 1.05 (95% CI 0.92 to 1.19) for vitamin B12, and 0.99 (95% CI 0.88 to 1.10) for retinol. Excluding NTD cases with known or suspected causes unrelated to vitamins, restricting the analyses to interviewed subjects, and excluding subjects whose specimens were collected after 15 gestational weeks confirmed that NTD case and control vitamin levels did not differ significantly. This population-based investigation in a low rate area demonstrated no relationship between maternal serum folate, vitamin B12, or retinol levels during pregnancy and the risk of NTDs.