Background: Maternal obesity confers increased risks of poor pregnancy outcomes. There are limited Australian data on the risk of birth defects associated with maternal pre-pregnancy obesity.
Methods: Population-based case–control study of 418 controls, 111 cases with heart defects (and of these, 38 had conotruncal heart defects), 27 with neural tube defects, 86 cases with urinary tract defects, 48 cases with orofacial clefts, and 20 with limb reduction defects. Maternal pre-pregnancy weight and height were self-reported.
Results: Women with pre-pregnancy obesity (body mass index 30+) had a twofold increased odds of having an infant with neural tube defects, conotruncal heart defects, orofacial clefts and limb reduction defects and 30–40% increase in heart defects generally and urinary tract defects. None of the estimates was statistically significant.
Conclusions: Our findings were consistent with similar, statistically significant studies in the literature. Weight reduction prior to pregnancy in obese women may be a means of primary prevention of birth defects.