Clinical inquiries. What treatments prevent miscarriage after recurrent pregnancy loss?

Progesterone produces a small but significant decrease in miscarriage among pregnant women with 3 or more unexplained pregnancy losses (strength of recommendation [SOR]: A, based on a meta-analysis of 3 small randomized controlled trials [RCTs] with wide confidence intervals). Human chorionic gonadotropin (HCG) reduces the rate of recurrent pregnancy loss among women with 2 or more unexplained pregnancy losses (SOR: B, based on a meta-analysis of 4 RCTs with significant methodologic weaknesses). Four types of immunotherapy are ineffective for preventing miscarriage (SOR: A, based on RCTs and systematic reviews of RCTs). Aspirin therapy is ineffective for preventing recurrent miscarriage for women who do not have an autoimmune explanation for previous pregnancy losses (SOR: A, based on RCTs).