Hypoxia-induced fetoplacental vasoconstriction in perfused human placental cotyledons.

Effects of maternal hypoxia on fetoplacental vascular resistance in the human placenta were investigated in an in vitro model in which single anatomic subunits (cotyledons) from term placentas were perfused at constant flow through both fetal and maternal circuits by means of a physiologic salt solution containing dextran. Acute reduction of oxygen tension in the maternal perfusate induced prompt fetoplacental vasoconstriction that recovered rapidly on restoration of oxygen to the perfusate. The response, hypoxic fetoplacental vasoconstriction, could be repeatedly demonstrated in the same cotyledon. The time course of hypoxic fetoplacental vasoconstriction was inversely related to oxygen tension of maternal arterial and maternal and fetal venous perfusates. Maternal and fetal venous perfusate pH and PCO2 did not change during the response. It is concluded that hypoxic fetoplacental vasoconstriction is triggered by decreased oxygen availability. It is suggested that hypoxic fetoplacental vasoconstriction may play a role in local regulation of human fetoplacental blood flow in vivo and may contribute to poor fetal prognosis in preeclampsia.