Physical activity and risk of neural tube defects.
OBJECTIVE
Owing to its association with known risk factors for neural tube defects (NTDs) and its impact on physiologic processes relevant to fetal development, physical activity was identified as a potential risk factor for NTD-affected pregnancy.


METHODS
Using data from a population-based case-control study of deliveries occurring in California from 1989 to 1991, we estimated the potential risk of having an NTD-affected pregnancy associated with variation in maternal physical activity. In-person interviews were conducted with 538 (88% of eligible) mothers of NTD cases and with mothers of 539 (88%) nonmalformed controls on average 5 months from the term delivery date. An index reflecting reported frequency and exertion level for six activity groups (e.g., jogging and running) was used to summarize each woman's physical activity level in the periconceptional period.


RESULTS
Unadjusted analyses indicated that compared to women considered inactive by this index, physically active women had 30-50% lower risk for NTD-affected pregnancies. After adjustment for several potential confounders and an evaluation of potential effect modification, results suggested that the association was restricted to women who did not take multivitamin/mineral supplements during the periconceptional period. Excluding mothers with reported medical problems did not substantially alter findings.


CONCLUSIONS
This study suggests that the benefits of physical activity may extend to reduction of NTD risk among certain subgroups of women.
Carmichael
Suzan L
SL
March of Dimes Birth Defects Foundation/California Department of Health Services, Oakland 94606-5226, USA. sca@cbdmp.org
Shaw
Gary M
GM
Neri
Eric
E
Schaffer
Donna M
DM
Selvin
Steve
S
D002140:California / Q000453:epidemiology; D005314:Embryonic and Fetal Development; D015444:Exercise; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007407:Interviews as Topic; D007590:Jogging; D016015:Logistic Models; D009436:Neural Tube Defects / Q000453:epidemiology* / Q000517:prevention & control; D011247:Pregnancy; D011295:Prenatal Care; D012307:Risk Factors; D040242:Risk Reduction Behavior; D012420:Running