Neural tube defects and associated low birth weight

To estimate the association between neural tube defects (NTDs) and low birth weight.

This was a retrospective cohort study of women undergoing ultrasound from 17 to 22 weeks from 1990 to 2008. Presence or absence of fetal NTD defined the two study groups. The primary outcomes were intrauterine growth restriction (IUGR), birth weight <10th percentile, and severe IUGR <5th percentile. Subgroup analysis was performed to observe if the association with IUGR persisted.

Of 66,956 women, 170 were found to have fetal NTD. Only the rate of advanced maternal age differed between the study groups. Fetuses with an NTD were at significantly increased risk for IUGR <10th percentile (adjusted odds ratio [aOR] 2.6, 95% confidence interval [CI] 1.8 to 3.9) and <5th percentile (aOR 2.8, 95% CI 1.9 to 4.3). The association persisted in subgroup analyses.

Fetuses with NTD are at increased risk for IUGR, suggesting that a policy of serial growth scans in cases with isolated NTD is justified.