Plasma and amniotic fluid concentrations of fibronectin during normal pregnancy

To ascertain the influence of pregnancy on plasma concentrations of fibronectin, we quantified plasma concentrations of fibronectin in 22 normal, pregnant women during the first, second, and third trimesters; at the time of delivery; and at six weeks and eight months postpartum, using a rapid, immunoturbidimetric procedure. Mean plasma concentrations of fibronectin rose significantly throughout pregnancy, and were significantly greater than umbilical cord plasma concentrations. Maternal plasma concentrations of fibronectin at six weeks postpartum were similar to those observed at the time of delivery, but returned to concentrations observed in nonpregnant women by eight months postpartum. No significant differences between concentrations of fibronectin in amniotic fluid obtained during the second and third trimesters of pregnancy were observed. Six-week postpartum values appeared to depend upon the type of infant feeding as values rose in bottle feeding but fell in breast-feeding mothers.