Amniotic fluid phosphatidylglycerol and real-time ultrasonic cephalometry.

The fetal biparietal diameter (BPD) was measured at the time of real-time ultrasound-directed amniocentesis in 159 cases and a phospholipid profile was obtained from the amniotic fluid. BPD measurements of 9.0, 8.7, and 9.2 cm were then compared with a lecithin/sphingomyelin (L/S) ratio greater than or equal to 2.0 for the ability to predict the presence of phosphatidylglycerol (PG) in the profile. The data from the diabetic and nondiabetic patients were analyzed separately. The results demonstrated that in the presence of a L/S ratio greater than or equal to 2.0 the BPD does not aid in the identification of amniotic fluid samples which contain PG in either the diabetic or nondiabetic groups. The data also confirmed previous findings that the BPD is not a reliable predictor of the L/S ratio. It is concluded that for the detection of PG in amniotic fluid, the use of real-time ultrasonic cephalometry cannot substitute for the performance of the phospholipid profile.