Prediction of fetal lung immaturity using gestational age, patient characteristics and fetal lung maturity tests: a probabilistic approach

Abstract

Objectives The lecithin/sphingomyelin (L/S) ratio and the lamellar body count (LBC) can be used to predict respiratory distress syndrome (RDS). Design We performed a retrospective cohort study among consecutive women who underwent amniotic Xuid sampling for the assessment of fetal lung maturity. Logistic regression was used to construct models for the prediction of RDS in three gestational age categories, with models based on clinical characteristics only, clinical characteristics and the LBC, and on clinical characteristics and L/S ratio. Results When amniotic Xuid was collected <30 weeks, the speciWcity of the LBC was 30% and the sensitivity 100%. Addition of the L/S ratio increased the speciWty to 60%, for a sensitivity of 100%. When amniocentesis was performed between 30 and 33 weeks, addition of the L/S ratio only marginally improved the performance of the LBC. Conclusions At a gestational age <30 weeks, the L/S ratio has additional value over the LBC. Above 30 weeks of gestation, single use of the LBC seems suYcient.

Arginase Activity and Lecithin/Sphingomyelin (L/S) Ratio in the Amniotic Fluid of Pregnant Women

“…Determination of the L/S ratio is by far the most widely used and accepted method to assess for fetal lung immaturity, [18,20,21]. Possible sources of enzymes found in amniotic fluid are mother's blood and placenta [25,26].…”

“…Surfactant is required to decrease surface tension within the alveoli thereby preventing alveolar collapse of the lung at the end of expiration [15][16][17][18][19]. The amount of these substances in the amniotic fluid changes towards the end of gestation in a manner related to fetal lung maturity [16,20]. The lecithin/sphingomyelin (L/S) ratio is a biochemical test for measuring the maturity of baby's lungs.…”

“…RDS is primarily a disease of premature infants with low birth weight, and is related to advanced maternal age, maternal diabetes and hypertension [20].…”

“…This cutoff has remained an accepted threshold for the determination of fetal pulmonary maturity. Infants who are born in the late preterm period (35-37 weeks' gestation) are at increased risk of respiratory morbidity compared with infants born at term, [16,19,20].…”

“…The probability of neonatal RDS using both gestational age and the L/S ratio may aid in clinical decision making concerning the timing of delivery [20].…”