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A woman in her 38th week of pregnancy is to have an amniocentesis to evaluate fetal maturity. The L/S (lecithin/sphingomyelin) ratio is 2:1. The nurse knows that this finding indicates.
a. fetal lung maturity
b. that labor can be induced.
c. the fetus is not viable
d. a non-stress test is indicated
Correct Answer: A. Lecithin and sphingomyelin are phosphilipids produced by the type II alveolar cells. The L/S ratio increases with gestation and a ratio of 2:1 indicates lung maturity.
An L/S ratio of 2:1 indicates lung maturity but there are several potential problems with this indicator; thus other parameters must also be measured. Meconium or blood in amniotic fluid alters the ratio and, despites a mature ratio in pregnancies complicated by diabetes, the neonate may still develop respiratory distress syndrome.
Viability refers to the fetus being capable of living outside the womb, now considered to be 25 weeks gestation due to advanced technology; L/S ratio is not used to measure viability.
A non-stress test is used to identify the fetus who may not be adapting well to the intrauterine environment; it does not indicate fetal maturity.
Posted in: MCN NCLEX
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