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Comparison of fetal maturity evaluation with ultrasonic biparietal diameter and amniotic fluid lecithin-sphingomyelin
Fetal head biparietal (BP) measurements by ultrasonic techniques and amniotic fluid lecithin-sphingomyelin (L/S) ratios were simultaneously determined (within 2 days) on 84 occasions in 72 women. Using the criteria for maturity of an L/S ratio of 2.0 or more or a BP measurement of 9.0 cm or more, there was agreement between these test results in 66.7% of the cases. The BP incorrectly predicted the L/S ratio 33.3% of the time, with a false positive rate of 27.3% and a false negative rate of 6.0%. If an L/S ratio of 1.5 were used as the critical determinant, the BP false positive rate remained high (9.5%). A high false negative error (21.4%) occurred if a BP value of 9.3 cm was used. These results suggest that ultrasonic BP measurements should not be used as the only criteria of fetal maturity in the management of high-risk pregnancies.
Fetal head biparietal (BP) measurements by ultrasonic techniques and amniotic fluid lecithin-sphingomyelin (L/S) ratios were simultaneously determined (within 2 days) on 84 occasions in 72 women. Using the criteria for maturity of an L/S ratio of 2.0 or more or a BP measurement of 9.0 cm or more, there was agreement between these test results in 66.7% of the cases. The BP incorrectly predicted the L/S ratio 33.3% of the time, with a false positive rate of 27.3% and a false negative rate of 6.0%. If an L/S ratio of 1.5 were used as the critical determinant, the BP false positive rate remained high (9.5%). A high false negative error (21.4%) occurred if a BP value of 9.3 cm was used. These results suggest that ultrasonic BP measurements should not be used as the only criteria of fetal maturity in the management of high-risk pregnancies.