Biopsy techniques to study the human placental bed

Background: The physiologic transformation of uterine spiral arteries in the human placental bed is essential for a healthy pregnancy. Failure of this transformation due to deficient trophoblast invasion is widely believed to underlie pregnancy complications such as preeclampsia, foetal growth restriction, miscarriage and preterm labour. Understanding of invasive behaviour and remodelling properties of trophoblasts in the uterine wall is essential in elucidating the aetiology of these pregnancy complications. However, there is a lack of satisfactory specimens of the placental bed to enhance our knowledge on the mechanisms that control trophoblast invasion. Several techniques can be used to obtain biopsies from the placental bed and sample handling can be executed differently depending on the research question. Methods: This systematic review provides an overview of all studies investigating the placental bed and sampling techniques used. Papers that described surgical techniques, specimen handling, complications and/or success rate of the placental bed biopsy procedures were included. Placental bed biopsies are an essential and feasible technique to study abnormalities in the placental bed associated with pregnancy complications. Results: Depending on the technique used the likelihood of sampling a spiral artery and trophoblast from the placental bed is 51%-78% per case, without significant complications. Conclusions: Caution is needed when interpreting data if the placental bed is subjected to labour. We propose a uniform sampling technique and conservation protocol for the study of the placental bed and provide tools for selection of the appropriate technique for future placental bed collections.