218 FETAL AND MATERNAL ARGININE VASOPRESSIN IN SPONTANEOUS OVINE PARTURITION

Abstract

In order to assess the possible correlation between plasma arginine vasopressin (AVP) levels and the process leading to the initiation of parturition, catheters were placed in maternal and fetal vessels of 11 pregnant ewes. Samples of blood withdrawn during a 20 day period preceding delivery and during parturition were analyzed for AVP by radioimmunoassay, pH, PaCO₂, and PaO₂.

Detectable levels of hormone were found throughout the interval prior to labor, fetal AVP 1.74 ± 0.18 pg/ml and maternal AVP 1.47 ± 0.10 pg/ml(mean ± S.E.). Daily fetal AVP levels taken during the 4 days prior to the onset of labor did not differ significantly from the levels during the preceding two weeks. Levels increased progressively during labor to reach peak values in cord blood (range 7.5 to 8000 pg/ml). There was no concomitant rise in maternal AVP. A persistent relationship between antepartum intrauterine asphyxia and increases in fetal AVP was noted. Antepartum and intra partum increases in fetal hormone correlated with decreases in fetal PaO₂ (r =-.790 and -.981).

It is concluded that the markedly elevated levels of AVP seen in both ovine and human cord blood are the result of intrapartum “stress” but are not related to the initiation of parturition.

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