Jill Durocher

Efficacy of a Low-sensitivity Urine Pregnancy Test for Identifying Ongoing Pregnancy After Medication Abortion at 64 to 70 Days of Gestation

March 5th, 2022
Medical Abortion
Whitehouse, K.C., Shochet, T., Lohr, P.A.

Contraception; 2022 Mar 5; S0010-7824(22)00052-X. doi: 10.1016/j.contraception.2022.02.005. Online ahead of print.

Objectives: We assessed whether a low-sensitivity pregnancy test is effective at identifying ongoing pregnancy after medication abortion at 64-70 days of gestation.

Study design: From October 2018 to March 2020, we performed a prospective observational study of participants in England and Wales undergoing medication abortion. Participants were scheduled to return to clinic 14 +/- 3 days after mifepristone administration to perform a low-sensitivity pregnancy test (human chorionic gonadotropin threshold of 1000 mIU/ml) and symptom checklist, and state whether they thought the abortion was complete. Clinicians also assessed the low-sensitivity pregnancy test and performed an ultrasound to determine abortion status. We calculated the sensitivity, specificity, negative and positive predictive value of the low-sensitivity pregnancy test (with and without a symptom checklist) for detecting ongoing pregnancy.

Results: We enrolled 757 participants. Thirty-one did not progress to abortion and 558 (76.9%) completed follow-up. Most (79.6%) attended per protocol; 22 (3.9%) attended earlier than 11 days and 92 (16.5%) later than 17 days. Thirteen participants (2.3%) had an ongoing pregnancy. The low-sensitivity pregnancy test correctly identified all the ongoing pregnancies (sensitivity=100%; specificity=84.8%; negative predictive value=100%; positive predictive value=13.5%). The symptom checklist alone had a sensitivity of 76.9% and negative predictive value of 99.4% for identifying ongoing pregnancies. Participants and clinicians agreed on the interpretation of the low-sensitivity pregnancy test 94.6% of the time.

Conclusions: Patient self-assessment of a low-sensitivity pregnancy test after medication abortion between 64 and 70 days’ gestation has a high sensitivity and negative predictive value for identification of ongoing pregnancy.