Fetal growth restriction (FGR); when a baby is measuring smaller than expected for gestational age; is one of the more complex diagnoses in high-risk pregnancy. Management depends heavily on how early in pregnancy it is diagnosed, what the umbilical artery Doppler shows, and whether other conditions like preeclampsia are present. This guide covers early and late FGR, surveillance protocols, delivery timing thresholds from SMFM Consult Series #52, etiology workup, and the questions that matter most at your appointments.
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Elizabeth Morgan MD · Fetal Growth Restriction Decision Guide
Your baby is measuring smaller than expected. Here is what that means.
Fetal growth restriction; often called FGR or IUGR; means a baby is not growing as expected for how far along the pregnancy is. The most important things to understand are why it is happening, how closely it needs to be watched, and when delivery becomes the right choice. The answers depend on your specific situation.
This takes about 10 to 15 minutes. At the end you will have a printable question list tailored to your situation. Nothing is stored or transmitted.
Not a substitute for clinical care. Evidence: SMFM Consult Series #52 (2020); ACOG Practice Bulletin #227.
Step 1 of 4 · Your Situation
Tell me about your diagnosis.
These answers shape everything that follows; the evidence summary, the surveillance discussion, and your question list. Skip anything you are unsure about.
How far along are you when FGR was diagnosed?
What has your umbilical artery Doppler shown?
How small is the baby? (Estimated fetal weight percentile if known)
Do you have preeclampsia or high blood pressure in this pregnancy?
Has a cause for the growth restriction been identified or discussed?
How are you feeling emotionally right now as you work through this?
Step 2 of 4 · Evidence and Context
What the evidence shows for your situation.
Tap any highlighted term for a definition. Expand any section to read more.
Step 3 of 4 · What Matters
Clarifying what feels most important.
These questions shape your personalized question list. There are no right answers.
Step 4 of 4 · Your Questions
Questions to bring to your care team.
Generated from your situation and what matters most to you. Add your own below.
Your own questions
What else do you need to know? These will appear on your printed list.
Support beyond the decision
Navigating a complex pregnancy is one of the most emotionally demanding experiences a person can go through. If you are struggling beyond the decision itself; with fear, grief, isolation, or weight that feels unmanageable; support is available.
Postpartum Support International:postpartum.net; helpline, provider directory, pregnancy and loss support
National Maternal Mental Health Hotline: 1-833-943-5746: 24/7, free, confidential
When a baby's estimated weight or abdominal circumference on ultrasound is below the 10th percentile for gestational age. Also called IUGR (intrauterine growth restriction). Not all small babies have FGR; some are constitutionally small. The distinction matters because true FGR carries higher risk of stillbirth and poor outcomes.
Severe FGR
Estimated fetal weight below the 3rd percentile. Associated with higher risk of adverse outcomes than FGR between the 3rd and 10th percentile. SMFM recommends weekly umbilical artery Doppler at minimum once severe FGR is identified.
Early-onset FGR
FGR diagnosed before 32 weeks of gestation. More commonly associated with placental insufficiency and maternal conditions like preeclampsia. Associated with more significant umbilical artery Doppler changes and more complex management. The single most important prognostic factor is gestational age at delivery.
Late-onset FGR
FGR diagnosed at 32 weeks or later. More common than early FGR. Umbilical artery Doppler is less likely to show the dramatic changes seen in early FGR; management relies more on fetal heart rate monitoring and clinical judgment. Delivery timing centers around 37 to 38 weeks in most cases.
Umbilical artery Doppler
An ultrasound measurement of blood flow in the umbilical cord artery. In FGR, placental resistance causes characteristic changes in the flow pattern. Normal flow is reassuring. Decreased end-diastolic flow suggests increased placental resistance. Absent or reversed end-diastolic flow indicates severe placental dysfunction and significantly increased risk of fetal deterioration.
AEDV (absent end-diastolic velocity)
The blood flow in the umbilical artery reaches zero between heartbeats. A serious finding that significantly increases surveillance frequency. Mean time from AEDV to delivery in one large study was approximately 13 days. SMFM recommends Doppler assessment 2 to 3 times per week once AEDV is detected.
REDV (reversed end-diastolic velocity)
The blood flow in the umbilical artery reverses direction between heartbeats. The most severe Doppler finding. Mean time from REDV to delivery approximately 4 days. SMFM recommends hospitalization, antenatal corticosteroids, intensive fetal heart rate monitoring, and consideration of delivery.
Ductus venosus (DV) Doppler
An ultrasound measurement of blood flow in a small vessel in the fetal liver that carries oxygenated blood from the placenta directly to the fetal heart. SMFM recommends against routine use in FGR management. However, many MFM centers use it selectively as an additional marker of fetal cardiovascular status, particularly in early FGR. The TRUFFLE study (a European randomized trial) found that DV Doppler-guided delivery timing was associated with better neurodevelopmental outcomes than CTG-guided delivery; this evidence is well-regarded but not yet incorporated into SMFM guidelines.
Cardiotocography (CTG) / Fetal heart tracing
Electronic monitoring of the fetal heart rate. In practice, fetal heart tracing is often the immediate trigger for delivery decisions in FGR with abnormal Dopplers; a non-reassuring tracing overrides any planned surveillance interval. SMFM recommends weekly CTG once FGR is diagnosed.
Cerebroplacental ratio (CPR)
The ratio of middle cerebral artery Doppler to umbilical artery Doppler. A low CPR suggests the fetus is redirecting blood flow to protect the brain ("brain sparing"). Some centers use CPR in late FGR as an additional factor in delivery timing decisions, particularly after 37 weeks. SMFM does not currently recommend it as a routine tool.
Biophysical profile (BPP)
An ultrasound assessment of fetal well-being that scores fetal breathing movements, body movements, tone, and amniotic fluid volume. Often combined with a non-stress test (NST). Used alongside Doppler in FGR surveillance. A score of 8 or 10 is generally reassuring; 6 or below warrants further evaluation.
Placental insufficiency
Inadequate function of the placenta to deliver oxygen and nutrients to the fetus. The most common assumed cause of FGR, particularly early FGR. Reflected by abnormal umbilical artery Doppler. Often associated with preeclampsia. There is no treatment that reverses placental insufficiency; management focuses on surveillance and timing delivery before fetal deterioration occurs.
Chromosomal microarray
A genetic test performed on fetal cells obtained via amniocentesis that detects small chromosomal deletions or duplications. SMFM recommends offering this at diagnosis of early FGR since up to 20% of cases are associated with chromosomal abnormalities. Results affect recurrence counseling and sometimes management.
CMV / Toxoplasmosis
Two infections that can cause FGR. Testing for these is typically done on amniotic fluid (obtained via amniocentesis) rather than maternal blood, because maternal serology alone has poor predictive value. SMFM recommends offering amniocentesis-based testing only if amniocentesis is already being performed for another reason (such as genetic testing).