Educational inequality in stillbirth: temporal trends in Québec from 1981 to 2009

OBJECTIVE: Educational inequality in stillbirth has been documented in high-income countries and the province of Québec, Canada, but temporal trends are poorly understood. Our objective was to determine time trends in inequality related to maternal education for all-cause and cause-specific stillbirth over the past three decades in Québec. METHODS: We included 2,397,971 live births and 9,983 stillbirths from 1981 through 2009 using Québec vital statistics. For each decade, we computed measures of inequality capturing relative (relative index of inequality, RII) and absolute (slope index of inequality, SII) differences between the least- and most-educated mothers for all-cause and cause-specific stillbirth, adjusting for maternal characteristics. RESULTS: Stillbirth rates decreased over time for all education levels. Absolute educational inequality (SII 2.5 per 1000 births, 95% CI 2.1-2.8; all periods combined) was stable over time, whereas relative inequality increased (RII(1981-1989) 1.8 vs. RII(2000-2009) 2.3). Absolute inequality decreased for stillbirths caused by placental abruption (SII(1981-1989) 0.6 vs. SII(2000-2009) 0.3), but increased for unspecified causes (SII(1981-1989) 0.2 vs. SII(2000-2009) 0.7). CONCLUSIONS: Absolute educational inequality in stillbirth persisted and relative inequality increased over the past three decades, despite an overall decrease in stillbirth rates. The decrease in absolute inequality for placental abruption was countered by an increase for unspecified causes. A better understanding of the underlying components of unspecified causes is needed to further address educational inequality in stillbirth.