796 Thai women who stopped using the long-acting injectable contraceptive 'Depo-Provera' (medroxyprogesterone acetate) and 125 women who had an intra-uterine device removed to have a planned pregnancy were followed-up to ascertain the delay between conception and the end of contraception, and to determine the proportion of women who did not conceive in the 2 years after discontinuation. The median delay before conception was 5.5 months plus the estimated duration of the effect of the last injection of depo-provera and 4.5 months after discontinuing the IUD. Since depo-provera acts for approximately 15 weeks, women can except a median delay to conception of around 9 months after their last injection. The proportions of women who did not conceive within 1 year and within 2 years of stopping contraception by the two methods were similar. There was no evidence to suggest that prolonged use of depo-provera increases the delay before conception, and the return of fertility among never pregnant ex-users resembled that of ever pregnant ex-users.
PIP: 796 Thai women (from the family planning clinic of the McCormick Hospital in Chiang Mai, Northern Thailand) who discontinued use of DMPA (depot medroxyprogesterone acetate) and 125 women who stopped using IUD to have a planned pregnancy were followed up to determine the proportion of women who did not conceive within 2 years of discontinuation, and to ascertain the delay between conception and end of contraception. The study was divided into 2 groups: retrospective (consisting of women who discontinued contraception before 12/74 to become pregnant) and prospective (those who stopped DMPA for aplanned pregnancy between 1/75 and 12/76. Life-table conception rates and standard errors were estimatedat monthly intervals and cumulatively over time; median delay before conception was calculated from cumulative rates. As both prospective and retrospective groups exhibited similar cumulative proportions conceiving, the 2 groups were combined for simplicity of presentation of data. Median delay before conception was found to be 5.5 months plus the estimated duration of the effect of the last injection of DMPA and 4.5 months after IUD discontinuation. As the effect of DMPA lasts for approximately 15 weeks, a median delay to conception of around 9 months after last injection can be expected. The proportion of women who did not become pregnant within 1 year and within 2 years of discontinuation of contraception was similar for both methods (DMPA: 21.8% at 1 year and 7.9% at 2 years; IUD: 21% at 1 year and 6.7% at 2 years). Prolonged use of DMPA also did not increase delay before conception, and return of fertility among never pregnant ex-users was similar to that of ever pregnant ex-users.