Maternal risks for very low birth weight infant mortality.

OBJECTIVE

To determine whether known maternal risk factors for low birth weight directly contribute to infant mortality among very low birth weight infants.

DESIGN

Retrospective population-based, case-control study.

SETTING

Four hospitals in the Oakland, California, area: one community, two private, one health maintenance organization.

PARTICIPANTS

All live-born singleton very low birth weight ( < 1500 g) infants born to Oakland residents over a 3-year period. Cases were infants who died before their first birthday, identified by computerized linkage of birth and death certificates. For each case, a surviving control was selected to match for birth weight, sex, and race. Forty matched pairs were identified in total.

OUTCOME MEASURES: Prevalence of maternal risk factors among cases versus controls.

RESULTS

After controlling for other factors known to influence either birth weight or infant mortality, maternal cocaine use (odds ratio [OR] = 5.43), prior infant death (OR = 27.14), and planned pregnancy (OR = 6.33) were significantly associated with the survival of very low birth weight infants.

CONCLUSIONS

Some maternal risk factors for low birth weight confer a survival advantage to very low birth weight infants. Our data reveal that maternal cocaine use is independently associated with survival among this subset of infants. Prior research supports the observed relationship as well as the scientific plausibility of a cocaine-mediated survival advantage among premature infants. Our study also showed both planned pregnancy and prior infant death to be independently associated with infant survival among this subset of infants, suggesting that maternal behaviors may play a role in determining birth weight-specific mortality. These data should be systematically evaluated to better define their relationship to infant mortality.