Amniotic fluid lecithin / sphingomyelin ratio

The amniotic fluid contains about 500 mg / L of fat and about 40 mg / L of phospholipid. In early pregnancy, there are many sphingomyelin, and its content does not change significantly during pregnancy. The content of lecithin as an alveolar surfactant is similar to sphingomyelin before 34 weeks of gestation, and it increases sharply after 34 weeks of gestation, so that the lecithin / sphingomyelin ratio is above 2 and this value can be regarded as fetal lung Maturity value. Fetal mature fetuses rarely develop respiratory distress syndrome after birth.