ObjectiveTo determine the degree of fetal endothelial involvement in preeclampsia by measuring fetal plasma concentrations of cellular fibronectin.MethodsIn a prospective cohort study, fetal plasma was collected at delivery from the chorionic plate arteries and veins in a convenience sample of 28 pregnancies complicated by preeclampsia and in 28 normal pregnancies. Stored plasma was assayed for cellular fibronectin using a sensitive and specific enzyme immunoassay. On the basis of a desired power of 0.8, α of .05, and expected fetal plasma cellular fibronectin values of 4 ± 2 μg/mL, 26 women were required in each group to detect a 40% difference between the groups. Results were compared using the unpaired Studentttest, χ2 analysis with Yates correction, and linear regression.ResultsThere was no statistically significant difference in fetal plasma concentrations of cellular fibronectin in women with preeclampsia compared with normal pregnant women, either in arteries (3.2 ± 1.1 and 2.9 ± 1.5 μg/mL;P= .33) or veins (3.3 ± 1.5 and 2.8 ± 1.6 μg/mL;P= .18). Plasma cellular fibronectin concentrations in fetal arteries correlated significantly with those in fetal veins (r= 0.45,P< .001), but not with those in maternal veins (r= 0.15,P= .27).ConclusionFetal plasma cellular fibronectin concentrations are similar in preeclamptic and normal pregnancies. We found no evidence that factors responsible for maternal endothelial involvement in preeclampsia are operative in the fetal circulation.