Accelerated pulmonary maturity as measured by the Lumadex-foam stability index test

The Lumadex-foam stability index test and lecithin:sphingomyelin (L:S) ratio were compared in the small preterm fetus. Amniotic fluid was obtained within 72 hours of birth from 70 high-risk patients whose infants were at 34 weeks' gestation or less and/or weighed less than 2000 g. Twenty-nine infants were small for gestational age. Eleven of the 41 appropriate for gestational age babies developed respiratory distress syndrome. Conclusions of the study were as follows: 1. The Lumadex-foam stability index test is an accurate, quantitative, and rapid measure of fetal lung maturity. 2. Growth retardation accelerates functional lung maturity in the preterm fetus. 3. The foam stability index value can discriminate between the small for gestational age and appropriate for gestational age fetus at 32 weeks' gestation or less and/or less than 1500 g birth weight. 4. The L:S ratio cannot discriminate between the small for gestational age and appropriate for gestational age fetus because the false-negative rate increases as fetal weight decreases.