Narrowing of sex differences in infant mortality in Massachusetts.

OBJECTIVES

To examine whether the improved survival of preterm infants has influenced the known male excess in infant mortality.

STUDY

DESIGN

We analyzed sex-specific infant mortality using linked birth and death certificates for all 619,811 live born infants in Massachusetts between 1989 and 1995.

RESULTS

Between 1989 and 1995 the male excess in infant mortality decreased by 50%, from 1.6/1000 to 0.8/1000 live births (LB). This narrowing resulted primarily from a more rapid decline in neonatal mortality among male infants (1.5/1000 LB) than among female infants (0.9/1000 LB). The largest declines in the male excess in neonatal mortality occurred among very premature infants (GA < or = 30 weeks) and resulted primarily from a more rapid decrease in male deaths from respiratory distress syndrome.

CONCLUSIONS

The narrowing of the sex difference in mortality between 1989 and 1995 suggests that newer treatments like antenatal steroids, and surfactants may have differentially benefited male infants.