CPM Certified Professional Midwife

Answer: D - The lecithin/sphingomyelin ratio is used to assess the maturity of the baby’s lungs. To measure the L/S ratio, a sample of amniotic fluid is obtained. The surfactant, which contains lecithin and sphingomyelin, is needed to reduce the surface tension of the alveolar lining, preventing alveolar collapse. This test is usually performed at 35 weeks’ gestation. The risk of the baby of developing neural tube defects may be determined as early as 12 weeks’ gestation through chorionic villi sampling. The volume of amniotic fluid may be obtained through sonogram. A contraction stress test is performed to determine the baby’s tolerance of labor.