Objectives The primary objective of this study was to determine whether intramuscular depot medroxyprogesterone acetate (IM DMPA) given at the time of misoprostol administration, 24–48 hours after mifepristone, affects the rate of continuing pregnancy. In addition, the study explored factors predictive of continuing pregnancy.

Design Case-control study based on database review of women who underwent early medical abortion (EMA) over a 4-year period.

Setting Single abortion service in Scotland.

Participants 5122 women who underwent an EMA within the timeframe of this study.

Main outcome measures Continuing pregnancies among women receiving IM DMPA were compared with those choosing other hormonal methods of contraception, non-hormonal contraception or no contraception at the time of misoprostol administration. Logistic regression was performed to assess the effects of demographic characteristics, gestation at presentation and method of contraception provided, on outcome of pregnancy.

Results A total of 4838 women with complete data were included, of which there were 20 continuing pregnancies (0.4%); 284 women were excluded due to missing data. There was no increased risk of a continuing pregnancy among women who initiated IM DMPA at the time of misoprostol administration (24–48 hours after mifepristone) compared with women who initiated no hormonal contraception at this time (RR 0.48; 95% CI 0.06 to 3.81). Gestation ≥8 weeks and previous terminations were factors associated with increased likelihood of continuing pregnancy.

Conclusions Women choosing IM DMPA after EMA can be reassured that IM DMPA can be safely initiated at the time of misoprostol administration 24–48 hours after mifepristone without an increase in the risk of a continuing pregnancy. Both increasing gestation and previous termination were factors associated with an increased likelihood of continuing pregnancy following an EMA.