Prediction of fetal growth based on maternal serum concentrations of human chorionic gonadotropin, human placental lactogen and estriol

Background. The purpose was to determine the usefulness of maternal serum concentrations of human chorionic gonadotropin (hCG), human placental lactogen (hPL) and estriol as predictors of fetal growth. Method. From a large cohort serum obtained serially at 17, 25, 33 and 37 weeks of gestation were analyzed for randomly selected pregnancies resulting in small for gestational age (SGA, n = 102) and non-SGA (n = 112) infants. Results. There were no significant correlations between birthweight ratio (ratio of birthweight to mean weight for gestational age) and hCG, but between birthweight ratio on one hand and estriol for all stages of pregnancy (r = 0.19-0.38, p < 0.01 - p < 0.001) and hCL except at 33 weeks (r = 0.11 - 0.40, p ns - p < 0.001) on the other. There were statistically significant, but small median differences and substantial overlaps between the SGA and non-SGA infants for hCG at 17 and 37 weeks, for hPL at 17, 33 and 37 weeks, and for estriol at all the stages of pregnancy. The sensitivity and positive predictive value of low hormone concentrations (below the 10th percentile) in predicting the birth of an SGA infant were in the range of 6 - 26% and 17 - 39%, respectively. The corresponding specificity and prediction of a non-SGA infant from normal levels were 91 - 93% and 85 - 88%. Conclusions. HPL and estriol, but not hCG concentrations, are positively related to the size of the fetus, but the relationships are too weak to be of predictive value in an unselected population.