The stability of phospholipids in amniotic fluid.

A systematic study of amniotic fluid phospholipids including phosphatidylcholine (PC, lecithin), saturated phosphatidylcholine, and phosphatidylglycerol was undertaken to evaluate the stability of these surfactant indices as a function of temperature and time. The purpose of the study was to determine optimum conditions for storage and for transport of specimens to centralized laboratories performing comprehensive analyses of amniotic fluid phospholipids for improved assessment of fetal lung development. Remarkable stability was found for the above phospholipids, as well as for the more commonly employed ratio of lecithin to sphingomyelin. We determined that room temperature more commonly employed ratio of lecithin to sphingomyelin. We determined that room temperature storage is acceptable for periods up to 24 hours; however, when longer delays before lipid extraction are anticipated, it is essential that specimens be frozen or that refrigeration or wet-ice storage (4 degrees C) be employed. Results of this study indicate that when amniotic fluid samples are stored frozen and strict quality control is maintained in analytic procedures, only minimal changes occur in phospholipid concentrations over 12 months.