A colorimetric method for amniotic fluid phospholipids and their relationship to the respiratory distress syndrome

A recently published work has stated that the amniotic fluid lecithin concentration is an accurate method of predicting the development of the respiratory distress syndrome (RDS). We have developed a simpler method for estimating amniotic fluid phospholipids, and 204 amniotic fluids from 120 pregnancies were studied. The level of hydrolyzable phospholibids (of which lecithin represents approximately 70 per cent in the third trimester) rises in the third trimester, but a signalling surge is not seen in compiled data. Four of five cases in which RDS did occur were found to have the expected low level of amniotic fluid hydrolyzable phospholipid just prior to birth. However, RDS did not occur in a large group of infants whose amniotic fluid hydrolyzable phospholipid concentrations were low. We, therefore, believe that, though this method would be reasonably valid as a determinant of time of delivery if high levels were found, low levels are not necessarily indicative that RDS will occur.