PGF and preeclampsia: ,16,25 In preeclampsia, the stressed syncytiotrophoblast is responsible for an overproduction of sFlt-1, leading to an excessive rise in maternal serum sFlt-1 levels starting from the 21st to 24th week of gestation, compared to women without preeclampsia.25, 26, 27 A corresponding decrease in PlGF serum levels was observed simultaneously.26