Comparison of maternal serum estriol and urinary estrogen determinations as indices of fetal health

Twenty-four hour urinary estrogens (UE) and the estrogen/creatinine ratio (E/C) are advocated as indices of fetal well being. Maternal serum estriol (SE3) determinations offer potential advantages. Serial values for each parameter were determined on samples from 20 normal pregnant women in the last trimester and their normal ranges established. Significant correlations (p < 0.001) were found between SE3 and UE (r = 0.56), SE3 and E/C (r = 0.63), and UE and E/C (r = 0.88). Serial values for each parameter from 31 complicated pregnancies (e.g., diabetes, toxemia, postmaturity, anencephaly) were also determined. Seven of 8 pregnancies, where all parameters were low, ended with delivery of compromised infants. Interpretive difficulties in the clinical use of the individual indices from the high-risk group were identified. A high incidence (22 per cent) of incomplete urine collections limited the value of UE data. Consistent high or low creatinine excretion by some patients and apparent independent variations in estrogen and creatinine clearance may lead to false inferences from E/C. SE3 levels were probably influenced by renal estrogen clearance as well as estrogen production, thereby restricting accurate interpretation of fetoplacental status in some cases. In most high-risk pregnancies, serial 24 hour UE, E/C, and total creatinine excretion provide adequate data to monitor estrogen metabolism as one parameter of fetal health.