The interactive effects of induced abortion, inter-pregnancy interval and contraceptive use on subsequent pregnancy outcome.

Prior induced abortion and outcome of the next pregnancy are investigated, allowing for two intervening and potentially confounding variables: 1) length of interval between the termination of the first pregnancy and the conception of the next (inter-pregnancy interval) and 2) the utilization of contraception during this interval. Results show that non-contracepting (susceptibility) intervals which immediately precede a subsequent pregnancy are significantly shorter following an induced abortion than those following a spontaneous abortion or delivery. A life table analysis of all susceptibility intervals confirmed this finding. To investigate outcome of subsequent pregnancy as influenced by preceding pregnancy outcome, inter-pregnancy interval and contraceptive use in the interval, a categorical linear model has been developed. Among non-contraceptors, the model indicates no differences in proportions of succeeding adverse outcomes (spontaneous abortion or low birth weight) regardless of inter-pregnancy interval and whether or not the preceding pregnancy had been terminated by an induced abortion. For the contraceptive users, however, proportions of adverse outcomes increased with length of inter-pregnancy interval, and, within each interval category, proportion of adverse outcomes was higher when the preceding pregnancy had terminated in an induced abortion.