Prospective cohort study of unselected nulliparous women with a nested randomised controlled trial of screening using the sFLT1:PlGF ratio, ultrasound and maternal characteristics and intervention using enhanced monitoring and early delivery: study protocol for the POPS2 cohort and randomised controlled trial

INTRODUCTION: Current UK guidelines recommend measurement of symphyseal fundal height and measurement of maternal blood pressure and urinalysis, with the aim of detecting women at increased risk of fetal growth restriction (FGR) and pre-eclampsia. Between 2008 and 2013, we conducted a prospective cohort study recruiting 4512 nulliparous women at the Rosie Hospital, Cambridge, where we performed serial ultrasonic imaging and serial blood sampling and generated a novel screening test for pre-eclampsia and FGR. The method involved measuring the ratio of two placental biomarkers (soluble fms-like tyrosine kinase receptor-1 and placenta growth factor) at ~36 weeks of gestational age (wkGA) and combining the result with maternal characteristics and ultrasonic imaging. Women who screened positive had a ~50% risk of a composite outcome, consisting of pre-eclampsia±delivery of a baby with a birth weight