PREPREGNANT WEIGHT IN RELATION TO RISK OF NEURAL-TUBE DEFECTS

Objective.-To examine the relation between prepregnant weight and the risk of neural tube defects (NTDs). Design.-Data were collected from 1 988 to 1994 in a case-control surveillance program of birth defects. S etting.-Study subjects were ascertained at tertiary care centers and b irth hospitals in the greater metropolitan areas of Boston, Mass, and Philadelphia, Pa, and in southeastern Ontario. Participants.-Cases wer e 604 fetuses or infants with an NTD identified within 6 months of del ivery. Controls were 1658 fetuses or infants with other major malforma tions identified within 6 months of delivery. For 1992 to 1994, there were 93 control infants without major malformations. Main Outcome Meas ure.-Relative risk of NTDs in infants or fetuses for different materna l weights. Results.-Relative to women who weighed 50 to 59 kg, risk of NTDs increased from 1.9 (95% confidence interval [CI], 1.2 to 2.9) fo r women weighing 80 to 89 kg to 4.0 (95% CI, 1.6 to 9.9) for women wei ghing 110 kg or more. When women were classified according to daily in take above or below the recommended level of 400 mu g of folate, appro ximate threefold increases in risk were estimated for the heaviest wei ghts in both groups. Intakes of 400 mu g of folate or more reduced ris k of NTDs by 40% among women weighing less than 70 kg, but no risk red uction was observed among heavier women. Conclusion.-The risk of NTDs increased with increasing prepregnant weight, independent of the effec ts of folate intake.