Objectives
To describe the distributional properties and assess the performance of placental growth factor (PlGF) measured in blood samples collected before 11 weeks’ gestation in prediction of preeclampsia.

Methods
The study population consisted of pregnant women included in the PRESIDE study (Preeclampsia Screening in Denmark) with a PlGF measurement from the routine combined first trimester screening (cFTS) blood sample collected at 8–14 weeks’ gestation. PRESIDE was a prospective multicenter study investigating the predictive performance of the Fetal Medicine Foundation (FMF) first trimester screening algorithm for preeclampsia in a Danish population. For the current study, serum concentration of PlGF in the cFTS blood samples was analyzed in batches between January and June 2021.

Results
A total of 8,386 pregnant women were included. The incidence of preeclampsia was 0.7% <37 weeks and 3.0% ≥37 weeks. In blood samples collected at 10 weeks’ gestation, multiples of the median (MoM) of PlGF were significantly lower in pregnancies with preeclampsia <37 weeks. However, PlGF MoM did not differ significantly between pregnancies with preeclampsia and unaffected pregnancies in samples collected before 10 weeks’ gestation.

Conclusions
Gestational age for PlGF samples might be expanded from 11–14 weeks to 10–14 weeks in risk assessment for preeclampsia using the FMF first trimester screening model. There is little evidence to support the use of PlGF collected before 10 weeks’ gestation.