Concentrations of soluble Fas in maternal serum and amniotic fluid during uncomplicated pregnancies

To determine, during normal pregnancy, maternal serum (MS) and amniotic fluid (AF) concentrations of soluble Fas (sFas), an apoptosis-suppressing molecule that might play a role in the apoptotic process. Soluble Fas levels might explain existing immunotolerance, fetal well being, and rupture of membranes at term.

Sixty-six healthy, nonsmoking, pregnant women (mean age 32.6 +/- 4.8 years) with uncomplicated singleton pregnancies (15 in the first trimester, 30 in the second trimester, and 21 at term vaginal delivery) and 20 healthy nonpregnant women (mean age 32.5 +/- 3.8 years) were included in the study.

MS and AF sFas concentrations were measured by a sandwich enzyme-linked immunosorbent assay, and parametric tests were used in the statistical analysis.MS and AF sFas concentrations significantly depended on gestational age (P < .0008 and P < .0002, respectively). MS concentrations were significantly lower in the first trimester than those in the second trimester (P <.003), those at term (P < .03), and those in nonpregnant controls (P < .005). AF concentrations decreased significantly at term compared with those in the second trimester (P < .0003). AF sFas concentrations in the second trimester and at term were significantly lower than respective MS concentrations (P < .00001).

MS sFas concentrations decreased significantly in the first trimester of pregnancy, possibly affecting semiallograft tolerance. In the second trimester, concentrations return to control levels and remain unchanged until delivery. AF sFas concentrations decrease at term compared with the second trimester, possibly indicating increased apoptosis in preparation for rupture of membranes.