Estimation of gestational age and maternal serum steroid concentrations: total estriol

Acute increases in maternal serum unconjugated estriol between 35 and 37 weeks of pregnancy have been reported to correlate predictably with gestational age. In this study estriol was measured by radioimmunoassay in an effort to define maturational surges. Statistically significant variations from predicted regression lines were not demonstrated in any individual patient or in grouped data.