Individual free fatty acids in amniotic fluid and in plasma of pregnant women.

Individual free fatty acids (FFA) were measured in 77 amniotic fluid samples and in 57 maternal plasma samples. Gestational age ranged from 16 to 40 weeks. Amniotic fluid FFA decreased from 20-4 +/- 6-0 mumol/l in the second trimester to 17-0 +/- 6-0 mumol/l in the last six weeks of pregnancy. This was almost entirely accounted for by a decrease in the concentration of free stearic acid, while oleic acid increased slightly. No correlation between amniotic fluid FFA and maternal plasma FFA was found in samples obtained on the same day. It is suggested that amniotic fluid FFA may partly derive from renal excretion by the fetus.