In a pregnant patient with poorly controlled diabetes, which test indicates fetal lung maturity?

• A. Presence of phosphatidylglycerol (PG)
• B. Lecithin/sphingomyelin (L/S) ratio 2:1
• C. Surfactant/albumin ratio of 50 mg/gm
• D. Phosphatidylserine (PS) presence

Answer: (A)

Fetal lung maturity is assessed by looking at surfactant components in amniotic fluid. In a pregnancy with poorly controlled diabetes, the most reliable indicator is the presence of phosphatidylglycerol in the amniotic fluid. PG appears later in surfactant maturation and its detection correlates well with adequate surfactant production by the fetal lungs, signaling lower risk of neonatal respiratory distress syndrome at birth.

While the lecithin/sphingomyelin ratio has been a traditional marker of maturity, maternal diabetes—especially when poorly controlled—can delay lecithin production due to fetal insulin effects, making the L/S ratio less dependable in predicting maturity in this setting. Other markers like the surfactant/albumin ratio or phosphatidylserine are less routinely used or not as specific for maturity, so they are not as informative here.