The association between major birth defects and preterm birth.

OBJECTIVE

To evaluate the association between preterm birth and major birth defects by maternal and infant characteristics and specific types of birth defects.

STUDY DESIGN

We pooled data for 1995-2000 from 13 states with population-based birth defects surveillance systems, representing about 30% of all U.S. births. Analyses were limited to singleton, live births from 24-44 weeks gestational age.

RESULTS

Overall, birth defects were more than twice as common among preterm births (24-36 weeks) compared with term births (37-41 weeks gestation) (prevalence ratio [PR] = 2.65, 95% confidence interval [CI] 2.62-2.68), and approximately 8% of preterm births had a birth defect. Birth defects were over five times more likely among very preterm births (24-31 weeks gestation) compared with term births (PR = 5.25, 95% CI 5.15-5.35), with about 16% of very preterm births having a birth defect. Defects most strongly associated with very preterm birth included central nervous system defects (PR = 16.23, 95% CI 15.49-17.00) and cardiovascular defects (PR = 9.29, 95% CI 9.03-9.56).

CONCLUSIONS

Birth defects contribute to the occurrence of preterm birth. Research to identify shared causal pathways and risk factors could suggest appropriate interventions to reduce both preterm birth and birth defects.