Determination of lamellar body phospholipids in amniotic fluid: a method to predict when the fetal lung becomes mature.

Lamellar body material was isolated by highspeed centrifugation from the amniotic fluids of 10 mildly diseased patients followed longitudinally and of 60 other women. Three stages of development were defined: (1) immature stage: the phospholipid concentration is less than 20 mumol/l and phosphatidylcholine (PC) is approximately 50%; (2) transitional stage: the phospholipid concentration is between 18 and 40 mumol/l, of which PC is approximately 75% and phosphatidylinositol (PI) 10%. Phosphatidylglycerol (PG) is absent or present at very low concentrations; (3) mature stage: the phospholipid concentration is above 40 mumol/l; its PC percentage is 75% or more. PG is present and the percentage of PI decreases. An increase in phospholipid concentration of 3.27 +/- (SD) 0.75 mumol/l/day was found during the transitional stage. The rate of increase enables us therefore to approximate the number of days that it will take before the fetal lung is mature.