Relationship of obstetric parameters to the concentration of pregnancy-associated plasma protein A

Plasma corticotrophin-releasing factor (CRF) in normal pregnancy

Corticotrophin-releasing factor (CRF) was measured directly in maternal plasma using an immunoradiometric assay (IRMA). In the first and second trimester CRF levels were within the non-pregnant range (mean 15 pg/ml). A total of 72 women was followed sequentially from 28 weeks until delivery and CRF levels rose from a median of 20 pg/ml at 28 weeks to 1320 pg/ml at 40 weeks and 1732 pg/ml during labour. There was a strong correlation (rs = 0.81, P less than 0.001) between gestational age and CRF levels. The rate of rise of CRF (pg/ml) per week was associated with weight gain (rs = 0.36, P less than 0.05) but with no other obstetric variable. There was an association between umbilical cord and maternal plasma CRF levels (rs = 0.54, P less than 0.01).

Placental protein measurements in complicated pregnancies. I. Intrauterine growth retardation

Maternal serum levels of human placental lactogen (hPL), schwangerschaftsprotein 1 (SP1) and pregnancy-associated plasma protein A (PAPP-A) were measured serially throughout pregnancy in 753 women who had a normal pregnancy when recruited during the second trimester. Thirty-three women were delivered of an infant with low birth-weight and with phenotypic features of intrauterine growth retardation (IUGR). The predictive value of an abnormal (less than 10th centile) hPL result (PVpos) in the identification of IUGR was between 28 and 32%, the sensitivity (36-54%) being greatest at 35 weeks gestation. The predictive value of a normal result (PVneg) was 87-96% at various stages of pregnancy, also greatest at 35 weeks gestation. For SP1, the sensitivity and predictive values were also greatest at 35 weeks gestation (PVpos, 20%; sensitivity, 32%; PVneg, 95%), but for PAPP-A these values were considerably less at all gestations. The trends in levels of hPL, SP1 and PAPP-A observed in individual patients with IUGR were not apparently related to any clinically recognizable feature of the pregnancy or the degree of fetal compromise, irrespective of whether the levels were within or outside the 80% confidence limits of the normal range or whether the levels fell from within the normal range. These data suggest that maternal hPL measurements are superior in the identification of IUGR in samples obtained at 30-35 weeks gestation.

Immunohistochemical localization of pregnancy-associated plasma protein A (PAPP-A) in placentae from normal and pre-eclamptic pregnancies

An immunohistochemical method was used to locate pregnancy-associated plasma protein A (PAPP-A) in the placenta and uterus. In addition to 10 placentae and basal plates from normal pregnancies, ranging in gestational age from 37 to 40 weeks, the following specimens were studied: three uteri obtained by hysterectomy during early pregnancy; and three placentae from patients with severe hypertensive pre-eclampsia. In early gestation, PAPP-A was localized in the villous cytotrophoblastic cell layer and the endometrial glands but was not found in the villous syncytiotrophoblast, the cytotrophoblastic cell columns or the decidual cells. On histochemical examination of placentae from cases of pre-eclampsia with hypertension, an increased number of villous cytotrophoblastic cells and so-called X-cells was observed. The monospecific antiserum to PAPP-A reacted strongly and evenly with the cytoplasm of these cells. The present study strongly suggests that the active production sites of PAPP-A are the villous cytotrophoblastic cells and the X-cells.

Serum PAPP-A in normal pregnancy: relationship to fetal and maternal characteristics

Pregnancy associated plasma protein A (PAPP-A) was measured in maternal serum by electroimmunoassay in 414 women (with subsequent normal pregnancy outcome) during the 38th week of pregnancy. PAPP-A levels were examined in relation to maternal and fetal characteristics, revealing a statistically significant relationship with maternal weight, placental weight, fetal sex and gravidity. The correlation of PAPP-A levels to fetal sex and gravidity could not be explained by differences in placental or maternal weight. Mean levels of PAPP-A were also not significantly different in relation to fetal sex.

Specific and reversible interaction between pregnancy-associated plasma protein A and heparin

An interaction between heparin and circulating pregnancy-associated plasma protein A (PAPP-A) has been observed. This interaction could be reversed by the addition of the specific heparin antagonist protamine sulphate. In the presence of heparin, crossed immunoelectrophoretic analysis revealed an alteration in the electrophoretic mobility of PAPP-A, while a significant increase (22 to 64 per cent, P less than 0.02) in measured levels of PAPP-A was seen in electroimmunoassays. These findings are discussed in relation to the optimal conditions for the precise measurement of PAPP-A.