Cystine Aminopeptidase Activity in Pregnancy

. Maternal cystine aminopeptidase activity (CAP) and total urinary oestriol excretion have been compared in 11 normal patients between 30 and 41 weeks gestation, in 9 patients with toxaemia of pregnancy and in 3 patients with a history of complication during the actual or previous pregnancy. The statistical correlation between maternal CAP and oestriol excretion in normal patients was poor ( r =0.32). In patients with pre‐eclampsia the results were as follows: low CAP levels generally were associated with low oestriol excretion, whereas with high or normal CAP values there were varying levels of oestriol. CAP levels in blood are only related to the function of the placenta, whereas the oestriol excretion is related to the condition of the whole fetoplacental unit. Therefore serial CAP assays cannot replace oestriol assays in assessing the condition of the foetus and placenta. However, in some patients where intrauterine fetal death occurred, decreasing CAP values were observed before there was a significant change in oestriol excretion. This indicates that decreased placental function might be observed at an earlier stage using CAP than using oestriol determinations. CAP assay is therefore justified as a valuable test alongside estimation of oestriol excretion in judging the condition of the placenta during the last trimester. As the methods of CAP assays are simple and reproducible, CAP can be used on a large scale for detecting and monitoring pregnancies at risk, in order to get a more diversified picture with respect to the condition of the fetus and placenta during the last trimester.