Fetal maturity cascade: a rapid and cost-effective method for fetal lung maturity testing.

One hundred ninety-three amniotic fluid samples were tested for fetal lung maturity using a maturity cascade scheme involving the sequential use of, in order, the shake test, fluorescence polarimetry, and lecithin: sphingomyelin (L:S) ratio. If any of these tests indicated maturity, the sequence was terminated and no further test was performed, and the fetus was considered mature. Seventy percent of the tests yielded mature values and of these, 85 (63%) required a shake test only, 37 (27%) had a shake test and a fluorescence polarimetry, and only 14 (10%) required all three tests. From these 193 amniocenteses, 111 patients delivered within 72 hours of the procedure. One of 94 infants had respiratory distress syndrome after a mature test (1% false maturity) and ten of 17 had respiratory distress syndrome after an immature cascade (41% falsely immature). This approach saves time and cost and by confirming immaturity with multiple tests only when necessary and may improve predictability of neonatal respiratory distress syndrome.