<prompt> True about lecithin - sphingomyelin ratio isConcentration of Lecithin and sphingomyelin before 34 weeks in amniotic fluid is equalConcentration 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 riseThere is increased risk of Respiratory distress syndrome if LS ratio is 2  <response>: Concentration of lecithin relative to sphingomyelin begins to rise at 32 - 34 weeks. L S ratio 2 suggests high risk of RDS. 