A diabetic multigravida is scheduled for an amniocentesis at 32 weeks gestation to determine the L/S ratio and phosphatidylglycerol level. The L/S ratio is 1:1 and the presence of phosphatidylglycerol is noted. The nurse’s assessment of this data is:
A. The infant is at low risk for congenital anomalies.
B. The infant is at high risk for intrauterine growth retardation.
C. The infant is at high risk for respiratory distress syndrome.
D. The infant is at high risk for birth trauma.
Correct Answer: C. The infant is at high risk for respiratory distress syndrome.
When the L/S ratio reaches 2:1, the lungs are considered to be mature. The Lecithin-to-Sphingomyelin Ratio (L/S ratio) is one of several methods for clinicians to assess fetal lung maturation. This biochemical test was first introduced in the 1970s, where a sample of amniotic fluid was collected via amniocentesis to determine the risk of the neonate developing respiratory distress syndrome (RDS). The sample was then evaluated, utilizing thin-layer chromatography to assess the size of lecithin relative to sphingomyelin.
Option A: The L/S ratio does not indicate congenital anomalies. Based on new guidelines, these indications no longer warrant testing the L/S ratio or performing other fetal lung testing modalities. One possible exception relates to inaccurate dating of the gestational age. If there is poor dating of the pregnancy and the delivery is to be planned between 32 to 39 weeks gestation, the clinician may consider testing for fetal lung maturity.
Option B: The infant is not at risk for intrauterine growth retardation. The main focus of testing the L/S ratio is to determine fetal lung maturity in an effort to decrease the risk of delivering a neonate with respiratory distress syndrome (RDS). RDS predominantly occurs in preterm infants less than 39 weeks gestation with increased risk with lesser gestational age.
Option D: The infant will most likely be small for gestational age and will not be at risk for birth trauma. The normal L/S ratio is 2.0 to 2.5 and is significant for appropriate fetal lung development. An L/S ratio of less than 2.0 is significant for immature fetal lung development. For patients who have poorly controlled diabetes, there was a discussion for the L/S ratio to be 3.0 due to elevated maternal glucose impacting the maturity of the developing fetal lungs.