Evaluating risk factors in recurrent pregnancy loss: A prospective cohort study and its impact on live birth outcomes

Recurrent pregnancy loss (RPL) affects 1-2 % of all couples trying to conceive and is a challenging heterogeneous condition. This study aimed to evaluate the prevalence and impact of various risk factors in patients suffering from RPL. We performed a prospective cohort study including patients at the tertiary RPL Unit in the Capital Region of Denmark between 1st January 2000 and 1st January 2023. The main outcome of the study was the first pregnancy after referral and whether the pregnancy was ongoing at least to the 22nd gestational week. A total of 2555 patients were included in the study, out of whom 1892 patients achieved a pregnancy after referral to the RPL Unit. This resulted in 1103 live births (58.3 %) and 718 pregnancy losses (37.9 %). Maternal age, BMI, smoking status and the number of prior pregnancy losses were negatively correlated with the likelihood of achieving pregnancy. Furthermore, maternal age, prior pregnancy losses, antiphospholipid syndrome (APS) and uterine malformations were associated with reduced birth rates. Patients with secondary RPL had a higher birth rate compared to those with primary RPL, and patients with APS treated with low-molecular-weight heparin (LMWH) demonstrated a significantly increased birth rate compared to untreated APS patients. These findings suggest that certain risk factors significantly impact the likelihood of achieving pregnancy and live birth following RPL, which can be used in patient guidance.