Congenital heart defects after maternal fever.

Objective: The purpose of this study was to evaluate whether maternal febrile illnesses in early pregnancy are associated with increased risk for congenital heart defects in the offspring and whether such risk is mitigated by multivitamin supplement use.

Study Design: From a multistate population-based case-control study (National Birth Defects Prevention Study), we compared maternal reports of first-trimester febrile illness from 7020 subjects with heart defects and 6746 unaffected control subjects who were born from 1997 through 2005. Relative risks were computed with no fever or infection during the first trimester as reference group and were adjusted for potential confounders.

Results: First-trimester febrile illness was reported by 7.4% of control mothers (1 in 13). Febrile genitourinary infections were associated with selected heart defects, particularly right-sided obstructive defects (odds ratios, >3) and possibly others, whereas common respiratory illnesses were associated with low-to-negligible risks for most heart defects. When risk estimates were elevated, they tended to be mitigated when multivitamin supplements had been taken in the periconceptional period.

Conclusion: The source of fever and the use of supplements appear to influence the risk for heart defects. This information can be helpful in counseling and research, in particular with regard to primary prevention.