Spina bifida phenotypes in infants or fetuses of obese mothers.

BACKGROUND

A twofold or greater risk of neural tube defect (NTD)-affected pregnancy has been associated with prepregnant obesity, where obesity was defined as body mass index (BMI) of >29 kg/m(2). Risks have been more elevated for spina bifida than for anencephaly.

METHODS

We investigated whether finer phenotypic classifications of spina bifida, in combination with other factors, were associated with a BMI of >29 kg/m(2). Data were derived from a case-control study of fetuses and infants with NTDs among 1989-1991 California births. Interviews were conducted with mothers of 277 spina bifida cases and 517 nonmalformed controls.

RESULTS

Women with a BMI of >29 kg/m(2) compared with those </=29 kg/m(2) revealed an odds ratio (OR) of 2.2 (95% confidence interval [95% CI] = 1.4-3. 3) for spina bifida in their infants and fetuses. Elevated risks were observed for each spina bifida subphenotype, and risks varied by subphenotype: open spina bifida, OR = 2.0 (1.2-3.1); closed (skin-covered), 3.3 (1.4-7.5); isolated, 2.2 (1.4-3.4); nonisolated, 1.9 (0.9-4.2); high, 4.5 (2.1-9.6); low, 1.9 (1.2-2.9); open/isolated/high, 7.1 (2.8-18.1); and open/isolated/low, 1.8 (1. 1-3.1). Risks were higher among female infants/fetuses and foreign-born Latinas, and for some phenotypes the risks were quite large, e.g., OR = 8.3 (2.9-23.6) for "closed" spina bifida among female infants/fetuses whose mothers were >29 kg/m(2) compared with males whose mothers were </=29 kg/m(2). Maternal periconceptional vitamin use was not observed to influence risk as greatly across phenotypes.

CONCLUSIONS

The observed pathogenetic heterogeneity of prepregnant obesity and spina bifida risks suggests that there are likely to be several biologic mechanisms underlying the association.