Residual placental blood volume after cesarean section: A scoping review

The overall aim of this scoping review was to map the existing literature on residual placental blood volume in cesarean sections as an indirect measure of placental transfusion. Multiple databases including Pubmed, Cochrane, Embase and Web of Science were searched for relevant studies published between 1972 and 2023. All studies on cesarean sections with term pregnancies and information on residual placental blood volume were included. The PRISMA checklist was used for guiding the writing of this report. The literature search resulted in 31 studies including 8337 neonates born by cesarean section. Only four studies specifically explored cord clamping time in cesarean section and following residual placental blood volume. All except one, showed a significant association between delayed cord clamping and decreased residual placental blood volume, indicating an increased placental transfusion to the infant. No difference was found between emergency and elective cesarean section. Inconclusive results appeared regarding association between placental weight, foetal weight, gravitation, uterotonics and residual placental blood volume. Delayed cord clamping time in cesarean section seems to be associated with a decreased residual placental blood volume indicating an increased transfusion to the infant. Due to the limited evidence revealing placental transfusion in cesarean section, further studies are needed to investigate the physiology of placental transfusion and to identify the optimal time of cord clamping at cesarean section.