Term human fetal umbilical vein oxygen content, placental weight, and maternal blood pressure

Abstract

The relationship of umbilical venous oxygen content to placental weight and mean maternal arterial blood pressure was investigated in 38 normal nonlaboring subjects undergoing elective cesarean section at 38.4 +/- 0.2 weeks (mean +/- SEM). In 14 subjects breathing room air, umbilical vein oxygen content was found to be a function of the lowest mean maternal arterial blood pressure (r = 0.48, P = 0.04), but not to placental weight. In 24 subjects breathing supplemental oxygen, umbilical vein oxygen content was not related to placental weight or lowest mean maternal arterial blood pressure. Fetuses attached to placentas less than 396 g had a higher hemoglobin concentration than fetuses attached to placentas greater than 396 g. This suggests the possibility of chronic in utero hypoxemia in human fetuses attached to small placentas.