O-001 Human Reproduction Keynote lecture: Progesterone for pregnant people with threatened miscarriage

Threatened miscarriage, characterized by vaginal bleeding in early pregnancy, affects approximately 25% of all clinical pregnancies. Progesterone supplementation, typically administered vaginally, is a common clinical practice aimed at preventing miscarriage in cases of threatened miscarriage. However, the evidence regarding the effectiveness of this intervention is conflicting and subject to varying interpretations. In a randomized controlled trial conducted in Queensland, Australia, we evaluated the efficacy of nightly 400 mg vaginal progesterone administration, initiated at the onset of bleeding and continued until 12 weeks gestation, in increasing live birth rates among women experiencing threatened miscarriage. Our study did not find evidence supporting a treatment effect of vaginal progesterone in enhancing live birth rates, nor did we find evidence that progesterone improves live birth rates in women with a history of two or more previous miscarriages. We conclude that routine use of progesterone for threatened miscarriage cannot be recommended. However, the potential therapeutic benefit of progesterone in women with threatened miscarriage following recurrent pregnancy losses warrants further investigation through dedicated clinical trials in this population.