RESUMEN
OBJECTIVE: The aim of this study was to assess the added value of the soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF) ratio for adjusting the periodicity of ultrasound examinations in early-onset fetal growth restriction (FGR) and small for gestational age (SGA). DESIGN: A prospective, observational study. SETTING: Tertiary referral hospital. POPULATION: One hundred and thirty-four single pregnancies with ultrasonographic estimated fetal weight (EFW) below the 10th centile between 20+0 and 31+6 weeks of gestation with antegrade umbilical artery flow. METHODS: The time from Doppler and sFlt-1/PlGF assessment to delivery was recorded and classified into four ranges: <1, <2, <3 and <4 weeks. MAIN OUTCOME MEASURES: Sensitivity (Sn), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV) of sFlt-1/PlGF values to predict the time to delivery. RESULTS: In the SGA cohort, the NPV calculated for an sFlt-1/PlGF cut-off value of 38 was 100% for delivery before 3 weeks, and 98% for delivery before 4 weeks after diagnosis (95% CI 0.89-1.00). In the FGR cohort, the NPV calculated for an sFlt-1/PlGF cut-off value of 38 was 100% for delivery before 2 weeks after diagnosis (95% CI 0.92-1.00). By contrast, more than 50% of cases with an sFlt-1/PlGF value of >85 required an elective delivery before 1 week. CONCLUSIONS: sFlt-1/PlGF values in early-onset SGA and FGR are predictive of the time to delivery and could be used for planning fetal surveillance, by reducing the frequency of ultrasound in cases with sFlt-1/PlGF < 38 and by providing closer follow-up in cases with sFlt-1/PlGF >85. TWEETABLE ABSTRACT: sFlt-1/PlGF values in early-onset SGA/FGR could be used in addition to Doppler for planning fetal surveillance.