Transversal and longitudinal lecithin-sphingomyelin ratios in amniotic and lung fluids of fetal lambs

Lecithin-sphingomyelin (L/S) ratios were measured in both amniotic and in lung fluids of fetal lambs. Around Day 130 of fetal age sudden increase of L/S ratio appeared in lung fluid. The amniotic L/S ratio increased only slowly as a consequence of which false negative values were obtained. A respiratory distress syndrome is to be expected when the lung fluid shows a L/S ratio less than 2. The L/S ratio of lung fluid is preferable to amniotic L/S ratio. In comparison with those of amniotic fluid the L/S ratios of lung fluid were significantly higher. Lung fluid secretion was measured daily. Large differences were seen among the lambs. Two days before delivery a striking decrease in the quantity of lung fluid production was noticed in all aminals.