Accounting for time: insights from a life-table analysis of the efficacy of medical abortion.

OBJECTIVE

Previously published analyses have ignored the temporal nature of medical abortion and calculated effectiveness as the proportion of abortions that succeed. By using life tables, we incorporate the important element of time to produce unbiased efficacy rates as well as afford insight into the medical abortion process.

STUDY

DESIGN

Using data on 6568 women from 6 previously published mifepristone-misoprostol medical abortion studies, we generated multidecrement life table efficacy curves and evaluated the cumulative probability of successful medical abortion.

RESULTS

Efficacy rates calculated using proportions are biased because of loss to follow-up. Compliance with the medical abortion regimen was high. More than 80% of abortions were complete within a week of receiving mifepristone. Success continued to improve thereafter. Most surgical interventions were unnecessary.

CONCLUSION

Follow-up visits can be scheduled within a week of receiving mifepristone; however, aspirations should not be performed routinely if the abortion is not complete.