Human chorionic somatomammotropin, estriol and oxytocinase as indexes of fetal growth.

A group of 56 women with high risk pregnancies were studied since the 32nd week of gestation. With the aim of obtaining reliable fetal growth indicators, maternal serum hCS, estriol and oxytocinase levels were determined. hCS and estriol were determined by specific radioimmunoassays and oxytocinase with a colorimetric method. Mean values obtained the week before delivery of both hormones and the enzyme were correlated with the weight of the newborns. The correlation coefficients were 0.30, 0.33 and 0.30 for hCS, estriol and oxytocinase respectively (Figs. 2, 3 and 4). The newborns were classified into two groups, small for date and adequate weight for gestational age. Maternal hCS level corresponding to newborns with adequate birthweight for their gestational age was 7.94 ug/ml. This value was statistically higher than that corresponding to the group of small-for-date newborns, which was 5.15 ug/ml (Fig. 5). Similar results were obtained when the maternal estriol levels were considered according to the birthweight (Fig. 7). The same analysis applied to oxytocinase values did not show statistically significant differences. Arbitrary critical levels were established for hCS and estriol at 7 ug/ml and 35 ng/ml respectively. When values were below these levels, newborns would have greater possibility of being small for dates (Figs. 6 and 8). The predictive value was best when both hormones were considered concomitantly (77%) (Fig. 9). These results indicate the suitability of considering hCS and estriol levels in order to assess fetal growth.