Umbilical artery Doppler ultrasound in pregnancy

What does the evidence say about umbilical artery doppler ultrasound during pregnancy?

1. SMFM recommends serial umbilical artery Doppler after fetal growth restriction is identified. It suggests weekly assessment for severe growth restriction or decreased diastolic velocity, two to three assessments per week for absent end-diastolic velocity, and hospital-level surveillance when flow is reversed. 1
2. SMFM links delivery timing to the whole fetal-growth-restriction picture: 37 weeks for decreased diastolic flow without absent or reversed flow, 33 to 34 weeks for absent flow, and 30 to 32 weeks for reversed flow. These are specialist recommendations, not rules based on a single home reading. 1
3. An updated Cochrane review of 19 trials involving 10,667 high-risk pregnancies associated fetal or umbilical Doppler use with lower perinatal mortality and fewer inductions and cesareans than no Doppler. Trial quality and protocol heterogeneity limited certainty, and the intervention included broader surveillance rather than one isolated measurement. 2
4. A systematic review of 42 studies and 18,282 low-risk or unselected pregnancies found absent or reversed end-diastolic flow was rare and reported in only six studies. Most evidence was observational and from higher-income settings, so it did not establish benefit from routine Doppler screening in low-risk pregnancies. 3
5. A reference study performed serial measurements in 590 uncomplicated pregnancies from 14 to 42 weeks and showed that Doppler ratios depend on gestational age. Its historical healthy cohort supplied normal ranges, not outcome evidence or a threshold that patients can interpret without clinical context. 4

Is umbilical artery doppler ultrasound safe in each trimester?

• First trimester. Umbilical artery Doppler is not a routine first-trimester reassurance scan. If very early growth concerns arise, the clinician first confirms dating, anatomy, and possible maternal, fetal, or placental causes before deciding which surveillance is informative.
• Second trimester. Early-onset fetal growth restriction before 32 weeks often prompts detailed ultrasound and specialist evaluation. Doppler values must be interpreted against gestational age because normal resistance indices change as pregnancy advances.
• Third trimester. Serial umbilical artery Doppler is most commonly used once growth restriction is established. Normal, decreased, absent, and reversed diastolic-flow patterns lead to different surveillance frequency and delivery discussions based on the full clinical picture.