Evaluation of the optical density determination of the amniotic fluid in assessing fetal lung maturity

ABSTRACT

Respiratory distress syndrome [R.D.S.] is the commonest respiratory disorder in the premature infant which accounts for a high incidence of neonatal death. R.D.S. is due to a deficiency of surface active material [surfactant] in the neonatal lung. This surfactant was only reliably assessed by measuring the Lecithin/sphingomyelin ratio [L/S] in the amniotic fluid. Amniotic fluid optical density [O.D.] at 650 nm was reported to be as reliable as L/S in assessing fetal Lung maturity. Fifteen pregnant women of the high risk group between 28 and 34 weeks were studied. L/S ratio and optical density at 650 nm of the amniotic fluid were estimated on all patients before and 48 hrs after 4 intra-muscular injections of betamethazone [6 mg every 12 hrs]. Six patients were delivered within 2 -6 days after the injection, one baby died of R.D.S. and the others survived. The remaining 9 patients passed safely through their pregnancies and delivered at term. Amniotic fluids with O.D. at 650 nm of 0.15 were found to have an L/S ratio over 2 while readings <0.05 corresponded to L/S ratio of about 1.3 and readings between 0.05 and 0.15 corresponded to L/S ration of 1.5. Betamethazone injections raised the O.D. [as well as the L/S ratio] from immature pre treatment values to mature post treatment values in 12 out of the 15 cases studied. O.D. readings at 650 nm is a simple, easy, fast and as reliable as the L/S ratio in deciding fetal lung maturity