Fetal Dopplers — umbilical artery, MCA, ductus venosus, uterine artery

It is the fetal medicine review clinic. A 28-year-old woman at 29 weeks has an estimated fetal weight on the 3rd centile with an umbilical artery pulsatility index above the 95th centile. The registrar in front of you asks: "When do I deliver?" The answer is the whole point of fetal Doppler — to convert a single worrying scan into a surveilled pregnancy and a defensible decision about the day and the hour. This topic teaches the four vessels, the sequence of deterioration, and the TRUFFLE logic that turns the waveforms into a plan.^[8]

Overview and definition

Fetal Doppler velocimetry measures blood-flow velocity waveforms in four vessels, each telling you about a different part of the feto-placental unit. The skill is sequencing them — the umbilical artery first, the middle cerebral artery second, the ductus venosus last — so you can read how far along the road to decompensation a fetus has travelled.^[1][8]

The indices you will be asked to name:

• Pulsatility index (PI) = (peak systolic velocity − end-diastolic velocity) / time-averaged maximum velocity. The most used index in modern practice; reported as a centile or multiples of the median (MoM) for gestation.^[8]
• Resistance index (RI) = (peak systolic − end-diastolic) / peak systolic.
• Systolic/diastolic (S/D) ratio = peak systolic / end-diastolic.

The vessels and what they tell you:

^{[8] [13]}

The cerebroplacental ratio (CPR) — the MCA-PI divided by the UA-PI — is a derived index that captures brain-sparing even when each vessel is individually borderline. A CPR below the 5th centile (or, in older formulations, below 1.0) is the more sensitive marker in late-onset FGR, where the umbilical artery is often normal.^[8][11]

References14ShowHide

1. [1]Lees CC, Marlow N, van Wassenaer-Leemhuis A, et al. 2 year neurodevelopmental and intermediate perinatal outcomes in infants with very preterm fetal growth restriction (TRUFFLE): a randomised trial Lancet, 2015.PMID 25747582
2. [2]Frusca T, Todros T, Lees C, Bilardo CM; TRUFFLE Investigators Outcome in early-onset fetal growth restriction is best combining computerized fetal heart rate analysis with ductus venosus Doppler: insights from the Trial of Umbilical and Fetal Flow in Europe Am J Obstet Gynecol, 2018.PMID 29422211
3. [3]Ganzevoort W, Thornton JG, Marlow N, et al. Comparative analysis of 2-year outcomes in GRIT and TRUFFLE trials Ultrasound Obstet Gynecol, 2020.PMID 31125465
4. [4]Mylrea-Foley B, Thornton JG, Mullins E, et al. Perinatal and 2-year neurodevelopmental outcome in late preterm fetal compromise: the TRUFFLE 2 randomised trial protocol BMJ Open, 2022.PMID 35428631
5. [5]Alfirevic Z, Stampalija T, Dowswell T Fetal and umbilical Doppler ultrasound in high-risk pregnancies Cochrane Database Syst Rev, 2017.PMID 28613398
6. [6]Stampalija T, Gyte GM, Alfirevic Z Utero-placental Doppler ultrasound for improving pregnancy outcome Cochrane Database Syst Rev, 2010.PMID 20824875
7. [7]Martins JG, Biggio JR, Abuhamad A Society for Maternal-Fetal Medicine Consult Series #52: Diagnosis and management of fetal growth restriction: (Replaces Clinical Guideline Number 3, April 2012) Am J Obstet Gynecol, 2020.PMID 32407785
8. [8]Lees CC, Stampalija T, Baschat AA, et al. ISUOG Practice Guidelines: diagnosis and management of small-for-gestational-age fetus and fetal growth restriction Ultrasound Obstet Gynecol, 2020.PMID 32738107
9. [9]Gordijn SJ, Beune IM, Thilaganathan B, et al. Consensus definition of fetal growth restriction: a Delphi procedure Ultrasound Obstet Gynecol, 2016.PMID 26909664
10. [10]Sovio U, White IR, Dacey A, et al. Screening for fetal growth restriction with universal third trimester ultrasonography in nulliparous women in the Pregnancy Outcome Prediction (POP) study: a prospective cohort study Lancet, 2015.PMID 26360240
11. [11]Roeckner JT, Pressman K, Odibo L, et al. Outcome-based comparison of SMFM and ISUOG definitions of fetal growth restriction Ultrasound Obstet Gynecol, 2021.PMID 33798274
12. [12]Mari G, Norton ME, Stone J, et al. Society for Maternal-Fetal Medicine (SMFM) Clinical Guideline #8: the fetus at risk for anemia—diagnosis and management Am J Obstet Gynecol, 2015.PMID 25824811
13. [13]Lees C, Stampalija T, Hecher K Diagnosis and management of fetal growth restriction: the ISUOG guideline and comparison with the SMFM guideline Ultrasound Obstet Gynecol, 2021.PMID 34077604
14. [14]Alfirevic Z, Stampalija T, Medley N Fetal and umbilical Doppler ultrasound in normal pregnancy Cochrane Database Syst Rev, 2015.PMID 25874722