[Cystine aminopeptidase and oxytocin in the plasma of pregnant patients with premature labor].

L-cystine aminopeptidase (CAP) activity in plasma was determined by spectrophotometry in 243 normal pregnant women in week 20-40 and 68 pregnant women with premature pains in week 28-37 of pregnancy. For significantly diminished CAP activity, pains and the subsequent premature birth correlated with infantile dystrophy, while in case of normal CAP activity the number of premature births was significantly less and newborns had eutrophic birth weights. In addition, radioimmunological measurements of oxytocin concentration in plasma were performed in ten pregnant women each of these groups. In women with premature pains, the oxytocin concentration was significantly higher than in normals. The present findings suggest that fetal oxytocin release might be the trigger signal for pains, thus causing premature birth. This signal might be chronically induced by a stress situation which manifests itself in hypotrophy of the newborns.