Comparison of six different ultrasonographic methods for predicting lethal fetal pulmonary hypoplasia

Nomograms of six different ultrasonographic fetal parameters were established by studying uncomplicated, singleton pregnancies, with well-established dates, between 16 and 40 weeks of gestation. The studied parameters could reflect fetal lung mass and included the following: chest circumference (CC), chest area (CA), chest area minus heart area (CA - HA), chest circumference/abdominal circumference ratio (CC X 100/AC), chest area/heart area ratio (CA/HA), and chest area minus heart area divided by chest area ratio [(CA - HA) X 100/CA]. The effect of ruptured membranes on these six ultrasonographic parameters was assessed by studying patients who had premature rupture of the membranes of less than 1 week's duration. It was found that premature rupture of the membranes is associated with increased frequency of CC, CA, and CA - HA measurements at or below the 5th percentile. However, in patients with premature rupture of the membranes all measurements were within the normal range for the three ratios. The efficacy of each of the six parameters was determined by studying 13 fetuses at high risk for development of lethal pulmonary hypoplasia. The (CA - HA) X 100/CA parameter had the best diagnostic accuracy (sensitivity 85%, specificity 85%, positive predictive value 83%, and negative predictive value 85%).