True about lecithin - sphingomyelin ratio is
Concentration of lecithin relative to sphingomyelin begins to rise at 32 - 34 weeks. L / S ratio < 2 suggests high risk of RDS.
Concentration of Lecithin and sphingomyelin before 34 weeks in amniotic fluid is equal
Concentration of Lecithin is more than sphingomyelin in amniotic fluid before 34 weeks.
After 32 to 34 weeks, concentration of sphingomyelin relative to Lecithin begins to rise
There is increased risk of Respiratory distress syndrome if L/S ratio is > 2