Prediction of preterm birth in women with fetal growth restriction – Is the weekly change in sFlt‐1/PlGF ratio or PlGF levels useful?

AbstractIntroductionTo assess the rate of change in soluble fms‐like tyrosine kinase‐1/placental growth factor (sFlt‐1/PlGF) ratio and PlGF levels per week compared to a single sFlt‐1/PlGF ratio or PlGF level to predict preterm birth for pregnancies complicated by fetal growth restriction.Material and methodsA prospective cohort study of pregnancies complicated by isolated fetal growth restriction. Maternal serum PlGF levels and the sFlt‐1/PlGF ratio were measured at 4‐weekly intervals from recruitment to delivery. We investigated the utility of PlGF levels, sFlt‐1/PlGF ratio, change in PlGF levels per week or sFlt‐1/PlGF ratio per week. Cox‐proportional hazard models and Harrell's C concordance statistic were used to evaluate the effect of biomarkers on time to preterm birth.ResultsThe total study cohort was 158 pregnancies comprising 91 (57.6%) with fetal growth restriction and 67 (42.4%) with appropriate for gestational age controls. In the fetal growth restriction cohort, sFlt‐1/PlGF ratio and PlGF levels significantly affected time to preterm birth (Harrell's C: 0.85–0.76). The rate of increase per week of the sFlt‐1/PlGF ratio (hazard ratio [HR] 3.91, 95% confidence interval [CI]: 1.39–10.99, p = 0.01, Harrell's C: 0.74) was positively associated with preterm birth but change in PlGF levels per week was not (HR 0.65, 95% CI: 0.25–1.67, p = 0.37, Harrell's C: 0.68).ConclusionsBoth a high sFlt‐1/PlGF ratio and low PlGF levels are predictive of preterm birth in women with fetal growth restriction. Although the rate of increase of the sFlt‐1/PlGF ratio predicts preterm birth, it is not superior to either a single elevated sFlt‐1/PlGF ratio or low PlGF level.