Estimating gestational age in the term pregnancy with a model based on multiple indices of fetal maturity

A prospective ultrasonographic study was conducted in 100 normal pregnant women with gestational ages that ranged from 36 to 42 weeks in which multiple biometric measurements were obtained. Dimensions of the distal femoral, proximal tibial, and proximal humeral epiphyseal ossification centers, as well as the placental and colonic grades, were also evaluated. A high statistical correlation was found between gestational age and each of the five variables (p less than 0.001). With a stepwise linear logistic regression analysis, we determined that gestational ages (36 to 39 weeks and 40 to 42 weeks) could be ascertained with a high probability with the use of a combination of the proximal humeral epiphysis and colonic grades. Probability estimates were not significantly affected by the addition of the distal femoral, proximal tibial epiphyses, placental grade, or amniotic fluid volume. From these data, probability prediction tables were generated. The results of this study provide an alternate method by which gestational age may be estimated in late pregnancy.