Intervillous space during uterine contractions in human subjects: an ultrasonic study

Six patients at term were examined by ultrasound during uterine contractions. The length, thickness, and surface of the placental area were found to increase during uterine contraction compared to relaxation. The conclusion is drawn that during uterine contractions the intervillous space is distended. During uterine contraction more maternal blood is available for exchange with the fetal compartment.