[Evaluation of the success of medical abortion by a plasma hCG control threshold]

In France, monitoring of the success of medical abortion is recommended 2 to 3 weeks after the procedure. However, there is no clear consensus on the modalities of this monitoring. The main objective of this study is to identify a threshold of serum hCG (human chorionic gonadotropin) control for medical abortions ≤7 weeks of gestation below which success can be confirmed without recourse to pelvic ultrasound.

This is a retrospective multicenter study conducted over a 14-month period. The serum hCG level, measured between the 15th and 25th day following the abortion, was compared with the results of the pelvic ultrasound performed at the follow-up visit. Ultrasound failure was defined as retention or persistent pregnancy.

Among the 624 women included, the failure rate was 22.3%, including 86.3% of retentions, 8.6% of pregnancies stopped and 5% of pregnancies progressed. Using a ROC curve, the threshold value of hCG found to exclude failure at 95% was 253 IU/l (AUC=0.9202, sensitivity=84.17%, specificity=85.95% and positive predictive value [PPV]=63%).

A serum hCG level ≤253 IU/l is sufficient to affirm the efficacy of medical abortion. However, since PPV is only 63% for this threshold, ultrasound should be reserved for women with high hCG levels.