Prediction of fetal growth deviation by ultrasonic biometry. II. Clinical application.

A previously developed mathematical formula for prediction of fetal growth deviation at birth by means of ultrasonic fetometry was applied to 505 unselected singleton pregnancies. The gestational age was assessed by measuring the fetal biparietal diameter (BPD) in the 17th week of pregnancy. In the 33rd and 38th week of pregnancy, BPD and the abdominal diameters (AD) were measured. In detecting fetuses small-for-gestational age (SGA) in the 33rd week, the ultrasonic diagnostic test had a nosological sensitivity of 77% and a nosological specificity of 78%. The nosological sensitivity and specificity for detecting fetuses large-for-gestational age (LGA) were 75% and 82%, respectively. The result was not improved significantly when the formula was applied to the total group in the 38th week. At the 33rd week examination risk groups with high prevalence of SGA and LGA fetuses were identified. When these groups were submitted to an additional examination in the 38th week, the prevalence of SGA and LGA fetuses in the new risk groups increased to 50%. At the 33rd week examination the predictive value of a negative test for SGA and LGA was 98%. Thus, the procedure described is well suited for general screening of pregnant women with ultrasound, and, combined with other biochemical and biophysical tests, makes possible a close clinical surveillance of the fetus at risk.