Circulating concentrations of sFlt1 (soluble fms-like tyrosine kinase 1) in fetal and maternal serum during pre-eclampsia

OBJECTIVE: We hypothesized that umbilical vein serum soluble fms-like tyrosine kinase 1 (sFlt1) concentration was augmented in pre-eclampsia. We also explored a possible association between fetal and maternal concentrations of sFlt1. STUDY DESIGN: At cesarean delivery, maternal serum samples from pre-eclamptic (n=38) and uncomplicated (n=32) pregnancies were obtained, as well as umbilical vein serum and amniotic fluid samples. ELISA for human sFlt1, vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) were performed. RESULTS: Median sFlt1 concentrations were elevated in pre-eclampsia compared to uncomplicated pregnancy, in umbilical venous serum (246 and 163 pg/mL, P=0.04), in maternal serum (9932 and 3417 pg/mL, P<0.001), as well as in amniotic fluid (51,040 and 33,490 pg/mL, P=0.03). A positive association between the fetal and maternal serum levels of sFlt1 was found in the pre-eclampsia group. Median PlGF concentration in the maternal serum was significantly lower in the pre-eclampsia group compared to the control group (82 pg/mL and 169 pg/mL, P<0.001). CONCLUSIONS: sFlt1 concentration is elevated in the fetal circulation in pre-eclampsia, but at a much lower level than in the maternal circulation. The results of our study do not support a substantial fetal contribution to the elevated circulating maternal sFlt1 protein concentration in pre-eclampsia.