Changes in placental ultrasonic appearance. I. Incidence of Grade III changes in the placenta in correlation to fetal pulmonary maturity.

Placental grading has been proposed as a substitute for amniotic fluid analysis for predicting fetal pulmonary maturity. The efficacy of placental grading was prospectively evaluated by grading the placenta at the time of 174 amniocentesis procedures done for determination of fetal pulmonary maturity. Grade III changes in the placenta were a rare finding that occurred in only 7% of the examinations performed. Placental grading proved to be insensitive in that it predicted pulmonary maturity in only 5% of pregnancies in which amniotic fluid analysis predicted a mature fetus. In addition, placental grading falsely predicted fetal pulmonary maturity in 42% of patients in whom Grade III placental changes were found. These findings suggest that the determination of Grade III changes in the placenta occurs too rarely to be of use in predicting fetal pulmonary maturity in the uncomplicated pregnancy. Incorrect prediction of pulmonary maturity by placental grading in the complicated pregnancy makes this test of little value in the management of high-risk pregnancy.