Narrowing of Sex Differences in Infant Mortality in Massachusetts

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Abstract
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 ≤ 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.