What is the right timing for ultrasound evaluation after pregnancy termination with mifepristone?

To determine the timing for ultrasound evaluation after medical termination of pregnancy (MTOP).

The records of 301 consecutive women who underwent MTOP between July 2010 and July 2011 were studied retrospectively. The follow-up protocol included ultrasound evaluation 2 weeks after MTOP. Surgical termination was offered when pregnancy was found to be ongoing, and either hysteroscopy/curettage or a repeat ultrasound 2 weeks later was offered when the ultrasound findings were suspicious for retained products of conception. Pathology reports were used to confirm the presence of retained products of conception.

Women with ultrasound findings suspicious for retained products of conception were significantly older than women with negative ultrasound findings (30.9±7.7 years vs 24.8±6 years, p<0.0001). Two weeks after MTOP, ultrasound findings were negative in 236 women and suspicious in 66 women. This rate declined as the interval between ultrasound evaluation and MTOP increased (up to 10 weeks). Of the 18 women (5.98%) who underwent hysteroscopy/curettage, pathology reports indicated that 15 (83.3%) had true residua.

At 2 weeks after MTOP, ultrasound findings suspicious for retained products of conception do not conclusively indicate failure of the procedure. Ultrasound evaluation should be repeated 4-6 weeks later (6-8 weeks after MTOP) in women with suspected residua before diagnosing failure of the procedure.