CPT® Code 83661

1. Indications

The fetal lung maturity assessment using the lecithin sphingomyelin (L/S) ratio is indicated in several clinical scenarios, particularly when there is a concern regarding the maturity of the fetus's lungs. The following are the specific indications for performing this test:

• Assessment of Lung Maturity: To evaluate the maturity of the fetal lungs before delivery, particularly in cases of anticipated preterm birth.
• Risk of Neonatal Respiratory Distress Syndrome (RDS): To determine the probability of the newborn developing RDS, also known as hyaline membrane disease, after delivery.
• Management of Premature Labor: To decide whether to suppress premature labor based on the maturity of the fetal lungs.
• Induction of Labor: To assess whether the fetal lungs are mature enough to allow for the induction of labor in patients with complications affecting the health of the mother and/or fetus.

2. Procedure

The procedure for conducting a fetal lung maturity assessment via the lecithin sphingomyelin (L/S) ratio involves several key steps, each critical to obtaining accurate results:

• Step 1: Amniotic Fluid Sample Collection A separately reportable sample of amniotic fluid is obtained from the patient. This is typically done through an amniocentesis procedure, where a thin needle is inserted through the abdominal wall into the uterus to collect the fluid surrounding the fetus.
• Step 2: Laboratory Analysis The collected amniotic fluid sample is sent to a laboratory for analysis. In the lab, the amount of lecithin and sphingomyelin in the fluid is measured. Lecithin is a component of pulmonary surfactant, while sphingomyelin is a non-pulmonary lipid that remains constant in concentration.
• Step 3: Calculation of L/S Ratio The laboratory performs thin layer chromatography to determine the L/S ratio. This involves comparing the levels of lecithin to sphingomyelin in the amniotic fluid. The result is expressed as a numerical ratio, which is crucial for interpreting lung maturity.

3. Post-Procedure

After the fetal lung maturity assessment is completed, the results of the L/S ratio are typically communicated to the healthcare provider. Based on the findings, further clinical decisions can be made regarding the management of the pregnancy. If the L/S ratio indicates that the fetal lungs are mature (greater than 2), the healthcare team may proceed with plans for delivery. Conversely, if the ratio suggests immaturity, additional monitoring and potential interventions to delay delivery may be considered. It is also important to monitor the patient for any complications following the amniocentesis procedure, such as infection or premature rupture of membranes.