Diagnosis of the respiratory distress syndrome by amniocentesis

Studies on 302 amniocenteses show that changes in phospholipids in amniotic fluid (PLAF) reflect those in the lung of the developing fetus. A sudden increase in lecithin concentration after 35 weeks heralds maturity of the pulmonary alveolar lining when respiratory distress syndrome will not occur should the fetus then be born. Clinical interpretation is made on a thin-layer chromatogram by inspection; a lecithin spot clearly larger than that of sphingomyelin marked pulmonary maturity in the fetus.