Changes in amniotic fluid lecithin-sphingomyelin ratio following maternal dexamethasone administration

The effect of dexamethasone on amniotic fluid lecithin-sphingomyelin ( L S) ratio was measured in 15 fetuses of 34 weeks or less of gestation. Six of the patients presented with premature rupture of the membranes. A rise in the L S ratio to mature levels (two or more) was observed 24 hours to 11 days after the start of treatment in 12 patients. In 2 patients (one second twin and one anencephalic fetus), no rise in L S ratio occurred. Of 12 cases which ended in premature delivery (29 to 35 weeks) only one infant, a second twin delivered at the thirtieth week with a posttreatment L S ratio of 1.4 weighing 1,240 grams, developed severe respiratory distress syndrome and died. It is suggested that dexamethasone accelerates fetal lung maturation by increasing surfactant synthesis or release, and this may be achieved as early as the twenty-eighth week of pregnancy.