The pulmonary system is among the last of the fetal organ systems to mature, both functionally and structurally. Race may affect the timing of fetal lung maturation: fetal lung maturity appears to be achieved earlier in gestation in blacks and South Asians .
Because the immature pulmonary system may not oxygenate the neonate adequately, preterm birth can lead to significant neonatal morbidity or mortality [2,3]. Therefore, fetal pulmonary maturity is sometimes assessed before iatrogenic preterm delivery and can be a factor in determining the timing of delivery in these cases. Several laboratory tests are available for this purpose . All involve testing amniotic fluid, which is an indirect assessment of the likelihood of lung maturity; direct studies of fetal pulmonary function are not possible.
This topic will discuss tests for assessment of fetal lung maturity. Clinical manifestations, diagnosis, treatment, sequelae, and prevention of neonatal pulmonary immaturity are reviewed separately. (See "Pathophysiology and clinical manifestations of respiratory distress syndrome in the newborn" and "Prevention and treatment of respiratory distress syndrome in preterm infants" and "Antenatal corticosteroid therapy for reduction of neonatal morbidity and mortality from preterm delivery".)
WHEN IS FETAL PULMONARY MATURITY TESTING PERFORMED?
Term — Elective term cesarean delivery should be scheduled for ≥39 weeks of gestation . Fetal pulmonary maturity can be inferred if:
●Review of the patient's prenatal record confirms a gestational age of ≥39 weeks of gestation. (See "Prenatal assessment of gestational age".)