Recurrent first trimester pregnancy loss: revised definitions and novel causes

Purpose of review First trimester pregnancy loss affects up to 15% of clinically recognized pregnancies. Whereas most couples will proceed to have successful subsequent pregnancies, 2-4% will suffer recurrent losses, often with no identifiable cause. In fact, up to 40-50% of patients suffering recurrent pregnancy loss (RPL) will have no identifiable cause for their losses. Whereas the high incidence of spontaneous fetal aneuploidy will ensure that this number will never fall to zero, its level suggests that additional causes and appropriate diagnostic testing await discovery. The definition, diagnostic work-up and appropriate interventions among patients with RPL remain controversial. Here, we will review those papers published in the last 1-2 years that improve our understanding of the definition of RPL, that confirm the utility of present testing paradigms or that pose novel causes and diagnostic approaches to patients with a history of RPL. Recent findings Standard definitions of RPL have been suggested by the American Society of Reproductive Medicine. Suggested potential diagnostic testing for RPL has been expanded to include male factors and new paradigms that address placental function, including the role of vascular endothelial growth factor, thrombosis and maternal-fetal immunology. Summary Standardized definitions for RPL and standardized approaches to initiating the RPL work-up will aid in study design and improve the applicability and implications of published findings. Appropriate investigation of novel causes for RPL may decrease the percentage of patients carrying the diagnosis of unexplained RPL.