Depomedroxyprogesterone acetate impact on mifepristone action during medication abortion

To evaluate outcomes by gestational duration in patients who did and did not receive depomedroxyprogesterone acetate (DMPA) concurrently with mifepristone for mifepristone-misoprostol medication abortion and estimate the impact of DMPA on mifepristone action.

In this secondary analysis of a retrospective study, we analysed treatment failure and continuing pregnancy as a reason for failure both overall and by gestational duration group. We assessed available literature to estimate that misoprostol alone would result in abortion in approximately 74% of pregnancies without mifepristone and calculated the impact of adding mifepristone to the treatment regimen and of DMPA on these outcomes.

More than half of the patients in each group had pregnancies ≤49 days gestation (no DMPA: 432/704 [61.4%]; DMPA 73/141 [51.8%], p = 0.04). Ongoing pregnancy rates increased with advancing gestational duration both with (p = 0.0005) and without (p = 0.04) concomitant DMPA administration. No individual gestational duration group demonstrated a significant difference in outcomes between patients that did and did not receive DMPA, likely because of small numbers in each group. Overall, concomitant DMPA with mifepristone increased the likelihood of an ongoing pregnancy by 25.3% of the expected rate if DMPA completely blocked all mifepristone action but only by 16.1% for patients with pregnancies ≤49 days gestation.

Ongoing pregnancy as the reason for medication abortion failure occurs more frequently with advancing gestation in patients that do and do not receive DMPA concurrently with mifepristone. DMPA may impact mifepristone variably by gestational duration, but larger studies are needed.