This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: New born infants, Subject name: Pediatrics
Foetal lung maturity is assessed by ____________ 
Select and explain. 
A. L/S ratio, B. Billirubin content of amniotic fluid, C. Ultrasound, D. Amniocentesis
A: L/S ratio
Answer: A: L/S ratio 
Explanation: 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