ABSTRACT Objective To describe the evolution of soluble fms‐like tyrosine kinase‐1 to placental growth factor (sFlt‐1/PlGF) ratio in the last 5 weeks prior to delivery in singleton pregnancy complicated by early‐onset fetal growth restriction (FGR), with or without pre‐eclampsia (PE). Methods This was a prospective observational cohort study of early‐onset FGR cases that underwent serial assessment of maternal serum sFlt‐1/PlGF ratio from diagnosis to delivery. Measurements were made at weekly intervals and within the last 48 h before birth. Absolute values and percentage increase between time intervals were computed, and previously described cut‐off values of 38 (suspicion of PE), 85 (aids diagnosis of PE) and 655 (high risk for imminent delivery) were used for analysis of the sFlt‐1/PlGF ratio. We compared findings between cases with early‐onset FGR only (n = 37) and those that additionally developed PE (n = 36). Results Overall perinatal survival was 63/73 (86.3%). A sFlt‐1/PlGF ratio above 38 was observed 4 weeks before delivery in most FGR‐only and FGR with PE cases (73% and 100%, respectively), but absolute values of sFlt‐1/PlGF were significantly higher in FGR cases with PE. Extremely elevated values of the ratio (≥ 655) within the last 48 h before delivery were found in 65% of cases of FGR with PE, but in only 8% of isolated FGR cases (P < 0.001). Conclusion Elevated sFlt‐1/PlGF was observed in most early‐onset FGR pregnancies from 4 weeks before delivery, and values were even higher if there was concurrent PE. However, serial measurements of the ratio were of limited value, being useful only to anticipate the need for imminent delivery in cases of FGR with PE when sFlt‐1/PlGF values ≥ 655 were reached. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.