Effect of centrifugation on amniotic fluid phospolipid recovery.

Amniotic fluid lecithin and sphingomyelin were determined quantitatively in 33 samples obtained throughout the last trimester. Each sample was divided into three parts and each part was centrifuged at different relative forces prior to extraction. It is shown that centrifugation always removes considerable amounts of both lecithin and sphingomyelin from the supernatant towards the end of pregnancy, but very little at the beginning of the last trimester. The fatty acid composition of amniotic fluid lecithin, studied by gas liquid chromatography, indicate that surface active lecithin is lost by centrifugation of the fluid prior to extraction.