Income inequality and pregnancy spacing.

We examined the relationship between county-level income inequality and pregnancy spacing in a welfare-recipient cohort in Washington State. We identified 20,028 welfare-recipient women who had at least one birth between July 1, 1992, and December 31, 1999, and followed this cohort from the date of that first in-study birth until the occurrence of a subsequent pregnancy or the end of the study period. Income inequality was measured as the proportion of total county income earned by the wealthiest 10% of households in that county compared to that earned by the poorest 10%. To measure the relationship between income inequality and the time-dependent risk (hazard) of a subsequent pregnancy, we used Cox proportional hazards methods and adjusted for individual- and county-level covariates. Among women aged 25 and younger at the time of the index birth, the hazard ratio (HR) of subsequent pregnancy associated with income inequality was 1.24 (95% CI: 0.85, 1.80), controlling for individual-level (age, marital status, education at index birth; race, parity) and community-level variables. Among women aged 26 or older at the time of the index birth, the adjusted HR was 2.14 (95% CI: 1.09, 4.18). While income inequality is not the only community-level feature that may affect health, among women aged 26 or older at the index birth it appears to be associated with hazard of a subsequent pregnancy, even after controlling for other factors. These results support previous findings that income inequality may impact health, perhaps by influencing health-related behaviors. Copyright 2004 Elseiver Ltd.