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Fetal growth restriction

Also known as Intrauterine growth restriction, IUGR, FGR. Detected in the second half of pregnancy.

Fetal growth restriction means a baby is measuring smaller than expected for its age, usually because the placenta is not delivering everything it needs to grow. Not every small baby is restricted; some are simply built small and perfectly healthy. Monitoring exists to tell the two apart, and to watch a truly restricted baby closely so that, if the placenta is struggling, delivery happens at the safest moment. You will usually feel nothing yourself, which is why prenatal visits and your baby's movements matter so much.

Know the warning signs When to call a provider
How common
Up to about 10%
Partly definitional; many small babies are healthy.
When
Second half of pregnancy
Found by measuring, usually after 20 weeks.
Urgency
Call your provider
Report any decrease in your baby's movements right away.
Outlook
Good with monitoring
Most mild cases do well with surveillance and timed delivery.

Understanding it

What is fetal growth restriction?

Fetal growth restriction, also called intrauterine growth restriction, means an estimated fetal weight below the 10th percentile for gestational age. What matters is not the small size itself but what can lie behind it: a placenta not delivering enough oxygen and nutrients for the baby to grow as it should.

The key distinction is between a baby that is small but healthy and one that is truly restricted. Some babies are constitutionally small, following their own steady curve. Others are small because something, most often the placenta, is limiting them. On a single measurement the two look alike, which is why growth is tracked over time and blood flow studied to separate them.

When growth is genuinely restricted, usually from placental insufficiency, the baby may be getting less oxygen, raising the risk of distress, preterm birth, and, in severe cases, stillbirth. The risk tracks with how small the baby is and what the Doppler studies show, which is why restricted babies are watched so closely.

For you, growth restriction usually causes no symptoms. It is found by measuring: a belly (fundal height) that lags, confirmed on ultrasound. Since you cannot feel your baby's growth, two things matter most from your side: keeping your prenatal appointments, and reporting any drop in movements right away.

Symptoms

What are the symptoms?

There are usually no symptoms you can feel. Growth restriction is found by measuring your belly and confirming on ultrasound. The one thing you can notice, and must report, is your baby moving less.

Early signs

  • Usually nothing that you can feel
  • A belly (fundal height) that measures smaller than expected for your dates
  • Sometimes a sense that your baby feels small or is not as active

Emergency signs — call 911

  • A noticeable decrease in your baby's movements, reported right away
  • Any decrease in movements: call now rather than waiting to test it yourself
  • Any bleeding or severe belly pain, which needs prompt evaluation

Why it matters

Risks to you and baby

Stillbirth

The most serious risk. It rises the smaller the baby is and when blood flow studies are abnormal. Close surveillance and timing delivery to the findings aim directly at reducing it.

Low oxygen and distress

A struggling placenta can leave the baby with less oxygen reserve, which can surface as distress during monitoring or labor and shapes when delivery is planned.

Preterm birth

Restricted babies are often delivered early, because the placenta is failing or because it is the safest course. Steroids are given ahead when an early birth is likely.

Newborn complications

Smaller babies can have more trouble with breathing, feeding, keeping warm, and low blood sugar after birth, and may need extra support.

Most mild cases do well

Most babies with mild growth restriction do well with monitoring and well-timed delivery. Many small babies are simply small and healthy.

How it's found

How is it diagnosed?

Growth restriction is suspected when the belly measures small and confirmed on ultrasound. Blood flow studies then gauge how well the placenta is working and how urgent things are.

Fundal height measurement

A tape measure from the pubic bone to the top of the uterus is a simple screen. A measurement that lags the dates prompts an ultrasound.

Ultrasound growth measurements

Measures the head, abdomen, and limbs to estimate weight and percentile, and checks the amniotic fluid. An estimated weight below the 10th percentile defines growth restriction.

Umbilical artery Doppler

Measures blood flow through the placenta. Worsening flow (elevated, then absent, then reversed) signals a failing placenta and prompts earlier delivery.

Antenatal testing

Non-stress tests and biophysical profiles check your baby's wellbeing between growth scans.

In the second half of pregnancy, when the belly measures small or you have risk factors. Diagnosis relies on ultrasound rather than on how you feel.

Treatment

How is it managed?

No treatment makes a baby grow on command, so care centers on watching closely and delivering at the safest time, guided most by the blood flow studies.

Treatment paths

Care means serial growth ultrasounds, Doppler blood flow studies, and antenatal testing to track wellbeing, with steroids if early delivery becomes likely. Timing is individualized: milder cases can often continue closer to term, while worsening blood flow prompts an earlier delivery to get ahead of the risk.

Monitoring

Repeat growth scans, Doppler studies, non-stress tests, and biophysical profiles are used, and you are asked to monitor and report your baby's movements.

Can it recur?

Growth restriction can recur, at roughly 20% to 30% depending on the cause. Future pregnancies are monitored earlier and more closely, and for those at high risk of placental disease, low-dose aspirin can lower the risk of preeclampsia and the related growth restriction.

What you can do

Can it be prevented?

  • Do not smoke

    Smoking is one of the clearest modifiable causes. Stopping is among the most effective things you can do to protect your baby's growth.

  • Low-dose aspirin if you are at risk of preeclampsia

    For people at high risk of preeclampsia or placental disease, low-dose aspirin lowers that risk and, with it, the growth restriction placental problems can cause. It is not used for isolated growth restriction without that risk.

  • Support the pregnancy and report changes

    Good nutrition, managing chronic conditions, keeping prenatal visits, and reporting any drop in movements all help catch it early.

Who is more at risk

Risk factors

Placental problems or a prior affected pregnancy
Placental insufficiency is the leading cause, and having had a growth-restricted pregnancy raises the risk of another.
High blood pressure and preeclampsia
Hypertensive disorders reduce blood flow to the placenta and are among the most common maternal causes.
Smoking, alcohol, and drug use
Each can limit the baby's growth and are important, modifiable risks.
Autoimmune conditions
Conditions such as lupus and antiphospholipid syndrome affect the placenta and increase risk.
Fetal and pregnancy factors
Chromosomal or genetic conditions, infections passed in pregnancy such as CMV, and carrying multiples all contribute.

Do not wait

When to call your provider or 911

  • Call right away if your baby moves less than usual, or the pattern changes.
  • Report any bleeding or severe belly pain promptly.
  • Keep all growth scans, Doppler studies, and monitoring appointments, since this is followed by measurement, not symptoms.
  • Tell your provider if you smoke, so you can get help stopping.
  • If you had a growth-restricted pregnancy before, ask early next time about closer monitoring and low-dose aspirin.

Talking to your team

Questions to ask your provider

  • Is my baby truly growth restricted, or small and healthy?
  • What do the Doppler blood flow studies show about the placenta?
  • How often will you check my baby's growth and wellbeing?
  • What is the plan and likely timing for delivery, and might I need steroids?
  • What should I do if I notice my baby moving less?
  • Do you know the cause, and does it change what to expect?

Keep reading

More on fetal growth restriction

All pregnancy guides articles

Good to Know

Fetal growth restriction FAQs

Common questions about fetal growth restriction, answered.

Does a small baby always mean something is wrong?

No. Some babies are constitutionally small and perfectly healthy; others are small because something, often the placenta, is limiting growth. A single measurement cannot tell them apart, so monitoring over time and blood flow studies are used.

What causes growth restriction?

Most often placental insufficiency. Other causes include high blood pressure and preeclampsia, smoking and substance use, poor nutrition, autoimmune conditions, infections in pregnancy, and chromosomal or genetic conditions in the baby.

Is it my fault, or something about my diet?

Usually not. Most cases reflect placental function or factors outside your control. Smoking is one clear modifiable cause, so stopping helps, but this is often nobody's fault.

What are Doppler studies, and why do they matter?

Doppler ultrasound measures blood flow through the umbilical cord and placenta, among the best ways to gauge how hard the placenta is working. Worsening flow is an early warning that guides when to deliver.

Will I have to deliver early?

Possibly. It depends on how small your baby is and what the Dopplers show. Mild cases often continue close to term; abnormal flow or a very small baby may mean earlier delivery, with steroids given ahead.

Will my baby catch up and be okay?

Most babies with mild growth restriction do well with close monitoring and well-timed delivery, and many small babies grow into healthy children. More severe restriction needs closer care, which the monitoring provides.

What can I do to help?

Do not smoke, eat well, manage chronic conditions, keep every appointment, and report any drop in movements immediately. If you are at high risk of preeclampsia, ask about low-dose aspirin.

Will it happen again next time?

It can, at roughly 20% to 30% depending on the cause. A future pregnancy is monitored earlier and more closely, and low-dose aspirin may be recommended if you are at risk of placental disease.

Medically Reviewed · Updated

Reviewed by Dr. Grace Lin, MD, FACOG · OB-GYN

Obstetrician-gynecologist focused on reproductive and sexual health for women: pregnancy, BV, yeast, trichomoniasis and HPV/cervical screening. Our editorial guidelines →

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