Clinical Outcomes of Isolated Abnormal Umbilical Artery Doppler Findings in Normally Grown Fetuses: A Retrospective Cohort Study.

BACKGROUND: Umbilical artery Doppler (UAD) is widely used to assess placental function in pregnancies complicated by fetal growth restriction (FGR), but the clinical significance of an abnormal UAD in a fetus that is normally grown at the time of diagnosis is less certain. This study describes the subsequent Doppler course and pregnancy outcomes of such cases. MATERIALS AND METHODS: We performed a retrospective cohort study at Luton and Dunstable University Hospital of pregnancies with abnormal UAD identified between January and December 2025. Abnormal UAD was defined as an umbilical artery pulsatility index above the 95th centile for gestational age, with absent or reversed end-diastolic flow also classified as abnormal. Normal growth was defined as AGA (appropriate for gestational age), with an EFW (estimated fetal weight) and/or AC (abdominal circumference) between the 10th and 90th centiles; pregnancies with established SGA (small for gestational age) or FGR at the index assessment were excluded. Electronic records were reviewed for Doppler progression, subsequent SGA/FGR, pre-eclampsia, mode of delivery, and neonatal outcomes. Descriptive statistics were used. RESULTS: During the study period, 1,372 UAD examinations were performed, and abnormal UAD was identified in 168 pregnancies. Fourteen pregnancies had incomplete follow-up, leaving 154 for analysis; 88/154 (57.1%) had normal fetal growth at the index abnormal UAD and formed the study cohort. UAD normalised on follow-up in 43/88 (48.9%) and remained abnormal in 45/88 (51.1%). Among pregnancies with persistent abnormal UAD, 11/45 (24.4%) subsequently developed SGA or FGR. Three of 88 pregnancies (3.4%) developed pre-eclampsia. The mean time to Doppler normalisation was 1.78 weeks. Among the persistent abnormal UAD group, 22/45 (48.9%) underwent induction of labour and 53/88 (60.2%) had caesarean births. Eight neonates (9.1%) were admitted to the neonatal intensive care unit. No stillbirths or early neonatal deaths were observed. CONCLUSION: Approximately half of isolated abnormal UAD findings in normally grown fetuses normalised on follow-up, while half persisted. Subsequent SGA/FGR occurred in 24.4% of the persistent group. These descriptive findings support continued surveillance after an isolated abnormal UAD and justify prospective studies with a comparator group and standardised management to define prognostic significance.