A 30-year-old pregnant woman visits her obstetrician for prenatal care and eventual delivery. The patient volunteers that two of her three children had "yellow jaundice" at birth. Her youngest girl had been severely jaundiced and had been given two blood transfusions. Prenatal laboratory tests indicate that the mother is blood type O, Rh negative, whereas her husband is blood type A, Rh positive. The obstetrician samples amniotic fluid at 36 weeks of gestation to ascertain whether the fetus is mature enough for preterm delivery. Quantitative analysis of which of the following was most likely used as an indicator of fetal lung maturity?
Immaturity of the lungs poses one of the most common and immediate threats to the viability of the low birth weight infant because the lining cells of the fetal alveoli do not differentiate until late pregnancy. Alveoli are maintained in the expanded state, in part, by the presence of pulmonary surfactant. This material, which is produced by type II pneumocytes, is a complex mixture of several phospholipids, 75% phosphatidylcholine (lecithin) and 10% phosphatidylglycerol. The concentration of lecithin increases rapidly at the beginning of the third trimester and, thereafter, rises rapidly to reach a peak near term. Maturity of the fetal lung can be assessed by measuring pulmonary surfactant released into the amniotic fluid. A lecithin-to-sphingomyelin ratio above 2:1 implies that the fetus will survive without developing respiratory distress syndrome. Alpha-fetoprotein (choice B) is used to monitor for anencephaly.Diagnosis: Erythroblastosis fetalis
Absorbance at 450 nm
Alpha-fetoprotein
Creatinine
Lecithin
Genetics