Short communication: the effect of mode of delivery on contractile function of placental arteries in vitro.

This study was designed to determine the effect of the mode of delivery on the in vitro assessment of placental blood vessel function. Twenty-two subjects with uncomplicated pregnancies, normal antenatal Doppler flow velocity waveforms and normal birth weights were recruited for the study. The 11 subjects who were delivered by elective caesarean section were matched with 11 controls, who had uncomplicated labours and spontaneous vaginal delivery. Two tertiary chorionic plate arteries were dissected free 1 h after delivery and mounted in a myograph. Cumulative concentration response curves were constructed to the thromboxane A2 analogue U46619, prostaglandin F2 alpha and angiotensin II. After a period of 12 h a further two vessels were mounted and a concentration response curve to U46619 was repeated to determine whether a delay of several hours after delivery would have an effect on the responses of these vessels. These placental arteries constrict to U46619, prostaglandin F2 alpha and angiotensin II in a dose-dependent manner. There was no statistical difference in the maximum contractile responses or pD2 values between the different modes of delivery. A delay in dissection of up to 12 h had no effect on the maximum response or pD2 with U46619. Therefore, contractile function of placental arteries is unaffected by mode of delivery or a delay in dissection.