Placental growth factor testing at 19–23 weeks of gestation as a guide to subsequent care in pregnancy: A prospective observational study

AbstractObjectiveTo determine whether serum placental growth factor (PlGF) at 19–23 weeks of gestation can improve the identification of risk for adverse outcomes.DesignProspective observational cohort study.SettingTwo English maternity units.PopulationUnselected singleton pregnancies attending routine ultrasound at 19–23 weeks of gestation.MethodsOutcomes ascertained by health record review. Diagnostic test properties evaluated clinical risk factors for pre‐eclampsia (according to National Institute of Care Excellence) or fetal growth restriction (according to Royal College of Obstetricians and Gynaecologists), low PlGF at 19–23 weeks of gestation (<5th percentile) or both.Main outcome measuresPre‐eclampsia, gestational hypertension, stillbirth, birthweight below third percentile or neonatal intensive care unit (NICU) admission for ≥48 h.ResultsIn 30 013 pregnancies, risk factors were present in 9941 (33.1%), low PlGF was present in 1501 (5.0%) and both (‘two‐stage’ screening) were present in 547 (1.8%) pregnancies. Risk factors detected 41.7%–54.7% of adverse outcomes, and could not meaningfully revise the risk (all positive likelihood ratios, +LR, <5.0; all negative likelihood ratios, −LR, ≥0.2). Low PlGF detected 8.5%–17.4% of adverse outcomes, but meaningfully increased risks (other than NICU admission) associated with delivery <37 weeks of gestation (+LR = 5.03–15.55); all −LRs were ≥0.2. ‘Two‐stage’ screening detected 4.2%–8.9% of adverse outcomes, with meaningful +LRs (6.28–18.61) at <37 weeks of gestation, except for NICU admission of ≥48 h, which had an +LR of 7.56 at <34 weeks of gestation; all −LRs were ≥0.2. No screening strategy meaningfully increased or decreased the detection of adverse outcome risk at term.ConclusionsClinical risk factor screening has a high screen‐positive rate and a poor detection of adverse outcomes. False positives cannot be reduced by PlGF testing at 19–23 weeks of gestation; therefore, this cannot be recommended as a useful strategy on its own.