Placental growth fActor Repeat sampling for Reduction of adverse perinatal Outcomes in women with suspecTed pre-eclampsia: study protocol for a randomised controlled trial (PARROT-2)

Background Pre-eclampsia is a complex pregnancy disorder, characterised by new or worsening hypertension associated with multi-organ dysfunction. Adverse outcomes include eclampsia, liver rupture, stroke, pulmonary oedema, and acute kidney injury in the mother, and stillbirth, foetal growth restriction, and iatrogenic preterm delivery for the foetus. Angiogenic biomarkers, including placental growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt-1), have been identified as valuable biomarkers for preterm pre-eclampsia, accelerating diagnosis and reducing maternal adverse outcomes by risk stratification, with enhanced surveillance for high-risk women. PlGF-based testing for suspected preterm pre-eclampsia has been incorporated into national guidance. The role of repeat PlGF-based testing and its effect on maternal and perinatal adverse outcomes have yet to be evaluated. Methods The PARROT-2 trial is a multi-centre randomised controlled trial of repeat revealed PlGF-based testing compared to repeat concealed testing, in women presenting with suspected pre-eclampsia between 22 +0 and 35 +6 weeks’ gestation. The primary objective is to establish whether repeat PlGF-based testing decreases a composite of perinatal severe adverse outcomes (stillbirth, early neonatal death, or neonatal unit admission). All women prior to enrolment in the trial will have an initial revealed PlGF-based test. Repeat PlGF-based tests will be performed weekly or two-weekly, depending on the initial PlGF-based test result, with results randomised to revealed or concealed. Discussion National guidance recommends that all women presenting with suspected preterm pre-eclampsia should have a single PlGF-based test when disease is first suspected, to help rule out pre-eclampsia. Clinical and cost-effectiveness of repeat PlGF-based testing has yet to be investigated. This trial aims to address whether repeat PlGF-based testing reduces severe maternal and perinatal adverse outcomes and whether repeat testing is cost-effective. Trial registration ISRCTN 85912420 . Registered on 25 November 2019