Foetal lung maturity is assessed by ____________

The presence of surfactant in amniotic fluid is evident of fetal lung maturity. L/S ratio determines the relative concentration of surfactant. L/S ratio is lecithin to sphingomyelin ratio and should be more than 2. There is an increased risk of respiratory distress syndrome when this ratio is less than 2. Reference : page 516 Textbook of Obstetrics Sheila Balakrishnan 2nd edition