Ultrasonic ratio of fetal thoracic to abdominal circumference: an association with fetal pulmonary hypoplasia.

Real time ultrasound was used in pregnant women who were considered to be at risk for development of pulmonary hypoplasia (n = 26). The population consisted of women who had either premature rupture of membranes (n = 16) or oligohydramnios (n = 10). The ratio calculated by comparing the fetal thoracic circumference to abdominal circumference was obtained in all cases within 10 days of delivery. This ratio correlated strongly with neonatal outcome. Multivariate regression models of neonatal outcome were developed to analyze the relationship of gestational age at which premature membrane rupture occurred, the duration of premature rupture, date of birth, and prenatal diagnosis. The addition of the thoracic circumference to the abdominal circumference ratio increased significantly the proportion of explained variability. Application of this ratio should be considered in evaluating fetal status in oligohydramnios and in the expectant management of premature rupture of membranes.