Influence of amniotic fluid volume on lecithin estimation in prediction of respiratory distress.

One hundred samples of amniotic fluid were obtained by amniocentesis from 82 patients at different stages of normal and abnormal pregnancies. The concentration of lecithin was estimated together with the volume of the amniotic fluid, using the dilution technique. Thus the total quantity of lecithin in any amniotic sac could be calculated. While confirming the findings of others that concentrations of lecithin below 3.5 mg/100 ml in the liquor immediately before delivery suggested that the baby was likely to develop respiratory distress syndrome, we found that in borderline cases the total amount of lecithin in the sac was of greater prognostic significance than the lecithin concentration.