When does lecithin appear in amniotic fluid?

Lecithin is a phospholipid that plays a crucial role in the development of surfactant in the fetal lungs, which is vital for reducing surface tension and preventing the collapse of alveoli after birth. The presence of lecithin in amniotic fluid is indicative of lung maturity.

Around 36 weeks of gestation, the production of surfactant increases significantly, leading to a notable rise in lecithin levels in the amniotic fluid. This increase correlates with improving fetal lung maturity, making 36 weeks a critical marker for assessing the readiness of the fetus for delivery. Prior to this gestational age, lecithin levels are typically lower, which means the lungs may not yet be fully mature. Thus, the timing of lecithin appearance at approximately 36 weeks aligns with the physiological development necessary for neonatal survival and respiratory function after birth.