Postamenorrheic versus postpartum strategies of contraception

The postpartum strategy of inserting an intra-uterine device shortly after a birth essentially eliminates the risk of conceiving again before starting contraception but maximizes the overlap between wearing time and postpartum anovulation when protection is not needed. In contrast, the postamenorrheic strategy of delaying insertion until right after the woman’s first menses all but removes overlap with anovulation but allows a chance of conception before start of contraception because sometimes an ovulation precedes the first menstruation. In this paper some algebra is developed and utilized to see which of the two strategies delays the next conception longer. The postamenorrheic strategy is found to have a slight advantage over the postpartum approach for a wide range of fecundability levels, lengths of anovulation, and rates of continuation of IUD. However this slight advantage presupposes that insertions are taking place at the exact time prescribed. When a progressively larger factor of procrastination is introduced, the advantage rapidly passes from the postamenorrheic to the postpartum approach. An explanation for the differing sensitivity of the two insertion strategies with respect to procrastination is derived from the results of an earlier analysis.