The Effects of Acute and Chronic Perinatal Stress on Plasma Vasopressin Concentration and Renin Activity at Birth

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Abstract
The effects of acute and chronic intrauterine stress on plasma vasopressin (AVP) concentration and renin activity (PRA) in the cord blood of 36 newborn infants were studied. AVP concentrations in the umbilical artery were significantly higher than those in the umbilical vein in all infants, except in those delivered by elective cesarean section after normal pregnancy. AVP concentrations in the umbilical arterial blood after normal term pregnancy and vaginal delivery (779 pg/ml, log mean) were higher than those in the cord blood of infants delivered vaginally after maternal hypertensive disease (198 pg/ml). Compared to the values of the latter group, the AVP values were significantly lower (39 pg/ml) in infants delivered by cesarean section without labor because of severe growth retardation and decreased heart rate variability. The group of normal term infants delivered by elective cesarean section after normal pregnancy had the lowest AVP concentrations (13 pg/ml). PRA in the umbilical arterial blood was not different from that in the umbilical venous blood. The highest mean level of PRA (14.5 ng/ml/h) was observed in premature infants delivered by cesarean section because of fetal growth retardation and pathological heart rate variability, and the lowest mean level in term infants delivered by elective cesarean section (3.4 ng/ml/h). PRA was significantly increased in term infants delivered vaginally after normal pregnancy (7.8 ng/ml/h) or after hypertensive pregnancy (11.7 ng/ml/h) in comparison to that of term infants delivered by elective cesarean section. At the age of 3 days the infants born after hypertensive pregnancy (11.8 ± 6.7 ng/ml/h, mean ± SD) had higher PRA in their peripheral blood than infants born after normal pregnancy (4.5 ± 2.3 ng/ml/h), but AVP concentrations were within the normal range (5.8 ± 2.3 and 4.0 ± 3.2 pg/ml). The acute stress of vaginal delivery seems to be the major determinant of AVP secretion at birth, whereas PRA is influenced rather by the chronic condition of maternal hypertensive disease or its treatment.

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