The concentrations of 2 substances in the amniotic fluid of pregnant women are graphed below. The two curves most likely correspond to which of the following?

Question

The concentrations of 2 substances in the amniotic fluid of pregnant women are graphed below.  The two curves most likely correspond to which of the following?

Quizplus · Accepted Answer

11ec160b_3750_8e01_9249_d94d2d1e5763_MD0001_00 Surfactant is an essential lipoprotein complex that decreases alveolar surface tension and facilitates alveolar expansion. Quantity and quality of surfactant increases throughout gestation and correlates with greater fetal lung maturity. Assessment of fetal lung maturity is not often indicated because infants of gestational age <32 weeks can be presumed to have immature lungs while those who are full term typically do not. However, a subset of patients may benefit from an evaluation of lung maturity to weigh the risks and benefits to the mother and fetus of preterm delivery versus continuing a medically complex pregnancy. Several markers of surfactant production and quality within amniotic fluid can help guide estimations of fetal lung maturity: Lamellar bodies are organelles within type 2 pneumocytes that store, transport, and secrete surfactant into the air-liquid interface of the alveoli. Increased lamellar body counts within the amniotic fluid are associated with increased surfactant production and lung maturity. Phosphatidylcholine (also known as lecithin [L]) and sphingomyelin (S) are lipid components of surfactant. They are produced in approximately equal amounts until the middle of the third trimester, at which point the phosphatidylcholine concentration increases sharply while the sphingomyelin level remains low, as represented by curves 1 and 2, respectively (Choices C and E). This change in composition (L/S >2) later in gestation reflects production of a more mature surfactant. Phosphatidylglycerol is a phospholipid component of surfactant that increases late in the third trimester, and its presence suggests advanced lung maturity. (Choices A and D) Amniotic fluid albumin concentrations normally decrease from mid-gestation to term. Albumin is not a clinically significant marker of fetal development. Educational objective: Fetal lung maturity correlates with increased quantity and improved quality of surfactant production. Amniotic fluid markers of maturity during late gestation include increased phosphatidylcholine (lecithin) and phosphatidylglycerol and low sphingomyelin. __________ References: Lecithin sphingomyelin ratio. (http://www.ncbi.nlm.nih.gov/pubmed/32809485)

The Concentrations of 2 Substances in the Amniotic Fluid of Pregnant