Fetal Growth Restriction Testing: How Doctors Monitor Babies Who Are Smaller Than Expected

The fetal growth restriction test during pregnancy helps doctors check whether your baby is growing normally and identify growth concerns early.

Hearing your doctor say that your baby is measuring smaller than expected can be worrying.

Many parents immediately wonder:

“Is my baby okay?”

“Will my baby continue to grow?”

“What tests will I need?”

“Does a small baby always mean something is wrong?”

Fortunately, being diagnosed with Fetal Growth Restriction (FGR) does not automatically mean your baby is unhealthy.

Modern prenatal care offers several safe and effective tests that help healthcare providers closely monitor babies who may not be growing as expected.

As a women’s health physiotherapist, I often reassure expectant mothers that additional monitoring is designed to keep both mother and baby safe.

In many cases, these tests simply help healthcare providers determine the best timing for delivery while allowing the baby to continue growing inside the womb for as long as safely possible.

Understanding fetal growth restriction testing can help reduce anxiety and make discussions with your healthcare team easier.

What Is Fetal Growth Restriction (FGR)?

Fetal Growth Restriction, previously called Intrauterine Growth Restriction (IUGR), occurs when a baby does not achieve its expected growth potential during pregnancy.

Generally, FGR is suspected when the estimated fetal weight falls below the 10th percentile for gestational age.

However, not every small baby has FGR.

Some babies are naturally small because of genetics and remain completely healthy.

True FGR usually occurs because the baby is not receiving enough oxygen or nutrients through the placenta.

According to the Society for Maternal-Fetal Medicine, FGR is associated with increased risks of perinatal complications and therefore requires close surveillance (Society for Maternal-Fetal Medicine Consult Series #52, 2020)

Why Is FGR Testing Important?

The primary goal of FGR testing is to determine whether the baby continues to thrive safely inside the womb.

Monitoring helps healthcare providers:

• Assess fetal well-being.
• Evaluate placental function.
• Identify babies at risk of complications.
• Decide how often surveillance is needed.
• Determine the safest time for delivery.

Early identification and appropriate monitoring significantly improve outcomes in pregnancies complicated by FGR.

Research shows that placental dysfunction is one of the leading causes of FGR and adverse pregnancy outcomes (Jaimie et al. 2025)

How Is Fetal Growth Restriction Diagnosed?

FGR is usually suspected during routine antenatal care.

Healthcare providers may notice:

• Fundal height measuring smaller than expected.
• Slow growth on ultrasound.
• Reduced fetal movements.
• Maternal risk factors such as hypertension or preeclampsia.

Once FGR is suspected, additional testing is recommended.

Growth Ultrasound Scans

Growth ultrasound is the cornerstone of FGR evaluation.

Serial growth scans assess:

• Head circumference (HC).
• Abdominal circumference (AC).
• Femur length (FL).
• Estimated fetal weight (EFW).

Rather than relying on a single scan, healthcare providers compare growth measurements over time.

This helps determine whether the baby is:

• Growing appropriately.
• Growing slowly.
• Experiencing progressive growth restriction.

Growth scans are usually repeated every 2 to 4 weeks depending on clinical circumstances.

Doppler Ultrasound Studies

Doppler ultrasound is one of the most important tests used in FGR.

Unlike standard ultrasound, Doppler studies evaluate blood flow between the mother, placenta, and baby.

Research demonstrates that Doppler surveillance improves outcomes in high-risk pregnancies complicated by placental insufficiency (Rocha et al. 2022)

Umbilical Artery Doppler

This is the most commonly performed Doppler assessment in FGR.

It evaluates blood flow from the placenta to the baby.

Abnormal findings may suggest:

• Placental insufficiency.
• Reduced oxygen delivery.
• Increased fetal risk.

According to the SMFM guideline, umbilical artery Doppler plays a central role in managing pregnancies affected by FGR (SMFM Consult Series #52, 2020).

Middle Cerebral Artery (MCA) Doppler

This test assesses blood flow to the baby’s brain.

When oxygen delivery decreases, the fetus may redirect blood flow toward vital organs such as the brain.

This phenomenon is known as the brain-sparing effect.

Abnormal MCA Doppler findings may indicate fetal adaptation to placental insufficiency.

Uterine Artery Doppler

Uterine artery Doppler evaluates blood flow from the mother to the placenta.

Abnormal uterine artery blood flow may increase the risk of:

• FGR.
• Preeclampsia.
• Placental insufficiency.

Amniotic Fluid Assessment

Healthcare providers routinely assess amniotic fluid levels in pregnancies affected by FGR.

Reduced placental blood flow can decrease fetal urine production, leading to low amniotic fluid levels.

Assessment may include:

• Amniotic Fluid Index (AFI).
• Single Deepest Pocket (SDP).

Low fluid levels may indicate worsening placental function.

However, fluid measurements are always interpreted alongside other surveillance findings.

Non-Stress Test (NST)

A Non-Stress Test evaluates fetal heart rate patterns and fetal movements.

During the test:

• Two monitors are placed on the mother’s abdomen.
• The baby’s heart rate is recorded.
• Heart rate accelerations are assessed.

A reactive NST is generally reassuring.

NSTs are commonly performed weekly or twice weekly in pregnancies complicated by FGR.

Biophysical Profile (BPP)

A Biophysical Profile combines ultrasound examination with an NST.

The BPP evaluates:

1. Fetal breathing movements.
2. Gross body movements.
3. Fetal muscle tone.
4. Amniotic fluid volume.
5. Fetal heart rate reactivity.

A reassuring BPP score generally indicates adequate fetal oxygenation.

Maternal Monitoring of Fetal Movements

One of the most important tests does not require any equipment.

Mothers are encouraged to monitor their baby’s usual movement pattern.

Reduced fetal movements should always be reported promptly.

Research has shown that maternal perception of reduced fetal movements may be associated with adverse pregnancy outcomes (Bekiou et al. 2020)

How Often Are FGR Tests Performed?

The frequency of testing depends on:

• Severity of growth restriction.
• Doppler findings.
• Gestational age.
• Maternal medical conditions.
• Overall fetal well-being.

Some pregnancies may require:

• Weekly growth surveillance.
• Twice-weekly NSTs.
• Frequent Doppler studies.
• Hospital admission for intensive monitoring.

A Physiotherapist’s Perspective: Looking Beyond the Numbers

As a women’s health physiotherapist, I often remind expectant mothers that FGR management focuses on trends rather than isolated measurements.

A single small measurement does not determine pregnancy outcomes.

Healthcare providers consider:

• Growth trends.
• Doppler findings.
• Fetal movements.
• Maternal health.
• Overall fetal surveillance.

Many babies diagnosed with FGR do very well when monitored appropriately.

Early-Onset vs Late-Onset Fetal Growth Restriction During Pregnancy

Healthcare providers often classify FGR into two broad categories.

Early-Onset FGR

Early-onset FGR is typically diagnosed before 32 weeks of pregnancy.

This form is often associated with:

• Severe placental insufficiency.
• Preeclampsia.
• Abnormal Doppler findings.
• Higher rates of preterm birth.

Because these babies are very premature, balancing the risks of prematurity against the risks of remaining in the womb can be challenging.

Early-onset FGR usually requires intensive monitoring and specialist care.

Late-Onset FGR

Late-onset FGR occurs after 32 weeks of pregnancy.

This type is more common and is often milder.

However, late-onset FGR can sometimes be more difficult to identify because standard Doppler findings may remain normal until later in the disease process.

What Do Abnormal Test Results Mean?

Abnormal surveillance findings do not automatically mean that your baby needs immediate delivery.

Instead, they help healthcare providers determine:

• Whether additional testing is required.
• How often surveillance should be performed.
• Whether hospital admission is necessary.
• When delivery may be safest.

Examples of concerning findings include:

Worsening Growth

Serial ultrasounds may show poor interval growth.

Low Amniotic Fluid

Reduced amniotic fluid levels may indicate worsening placental function.

Abnormal Doppler Studies

Abnormal umbilical artery Doppler findings may suggest increasing placental resistance.

Non-Reassuring NST or BPP

Abnormal fetal surveillance results may indicate reduced fetal oxygenation.

Healthcare providers interpret all findings together rather than relying on a single result.

Hospital Admission in FGR

Some pregnancies complicated by FGR require hospital admission.

Reasons may include:

• Severe growth restriction.
• Abnormal Doppler findings.
• Maternal preeclampsia.
• Non-reassuring fetal surveillance.
• Need for daily monitoring.

Hospital admission allows:

• Frequent fetal assessment.
• Maternal monitoring.
• Timely intervention if the baby’s condition changes.

According to the Society for Maternal-Fetal Medicine, pregnancies complicated by severe FGR and abnormal Doppler studies often require closer inpatient surveillance (SMFM Consult Series #52, 2020).

How Do Doctors Decide When to Deliver?

One of the most difficult decisions in Fetal Growth Restriction management in pregnancy is determining the optimal timing of delivery.

Healthcare providers aim to keep the baby inside the womb for as long as it remains safe.

However, if placental function deteriorates significantly, delivery may offer the safest outcome.

Delivery decisions consider:

• Gestational age.
• Estimated fetal weight.
• Doppler findings.
• NST and BPP results.
• Maternal health.
• Presence of preeclampsia.

The timing of delivery is highly individualised.

Research has shown that careful surveillance and appropriately timed delivery significantly improve outcomes in FGR pregnancies (Danciu et al. 2025)

Does FGR Always Mean a Cesarean Birth?

No.

Many women with FGR deliver vaginally.

The mode of delivery depends on:

• Fetal condition.
• Gestational age.
• Fetal heart rate patterns.
• Obstetric factors.
• Maternal health.

However, severe FGR with abnormal Doppler findings may increase the likelihood of cesarean delivery.

Your healthcare provider will discuss the safest delivery plan based on your individual circumstances.

Can You Improve Fetal Growth?

Many mothers understandably ask whether they can increase their baby’s growth.

Unfortunately, once true placental insufficiency develops, there are limited proven methods to accelerate fetal growth.

However, mothers can support overall pregnancy health by:

• Attending all antenatal appointments.
• Taking prescribed medications.
• Managing blood pressure and diabetes.
• Avoiding smoking and alcohol.
• Eating a balanced diet.
• Resting when advised.

As a women’s health physiotherapist,

I also encourage gentle, medically approved physical activity, stress management, and adequate sleep to support maternal well-being.

Limitations of FGR Testing

Although fetal surveillance has significantly improved pregnancy outcomes, no test is perfect.

FGR testing cannot:

• Guarantee a complication-free pregnancy.
• Predict labour onset.
• Eliminate all risks.
• Determine long-term developmental outcomes with certainty.

False-positive and false-negative results may occur.

Therefore, healthcare providers interpret all surveillance findings within the broader clinical picture.

A Physiotherapist’s Perspective: Looking After Emotional Health

Repeated scans and frequent monitoring can be emotionally exhausting.

Many women describe feeling anxious between appointments.

If you are experiencing significant stress, consider:

• Speaking openly with your healthcare team.
• Seeking support from family and friends.
• Practising relaxation breathing exercises.
• Participating in pregnancy-safe physical activity if approved.

Remember that additional surveillance is intended to support the healthiest possible outcome for you and your baby.

Questions You May Want to Ask Your Doctor

Consider asking:

• How severe is my baby’s growth restriction?
• Are my Doppler studies normal?
• How often will I need monitoring?
• Will I require hospital admission?
• When might delivery be recommended?
• What symptoms should prompt urgent review?

Writing down your questions before appointments can help reduce anxiety and improve understanding.

Conclusion

Fetal Growth Restriction testing plays a vital role in modern pre-pregnancy care.

Through a combination of ultrasound scans, Doppler studies, fetal surveillance tests, and maternal monitoring, healthcare providers can closely assess fetal well-being and determine the safest timing for delivery.

Although receiving an FGR diagnosis can feel overwhelming, many babies affected by growth restriction have excellent outcomes when monitored appropriately.

As a women’s health physiotherapist, I encourage expectant mothers to remain engaged in their care, attend all appointments, and communicate openly with their healthcare team throughout pregnancy.

Frequently Asked Questions (FAQs)

1. What tests are used to diagnose Fetal Growth Restriction?

Healthcare providers use growth ultrasound scans, Doppler studies, amniotic fluid assessment, NSTs, BPPs, and fetal movement monitoring to diagnose and monitor FGR.

2. How often will I need monitoring if my baby has FGR?

The frequency of monitoring depends on the severity of growth restriction, Doppler findings, gestational age, and overall fetal well-being. Some pregnancies require weekly or twice-weekly assessments.

3. Does FGR always mean my baby will be delivered early?

No. Many babies with mild FGR remain safely in the womb until near term. Delivery timing depends on fetal monitoring results and placental function.

4. Is Doppler ultrasound important in FGR?

Yes. Doppler ultrasound is one of the most important tests in FGR because it evaluates blood flow between the placenta and baby.

5. Should I monitor fetal movements if my baby has FGR?

Yes. Monitoring your baby’s usual movement pattern remains extremely important. Any significant reduction in movements should be reported immediately.

6. Can babies with FGR be healthy?

Yes. Many babies diagnosed with FGR have excellent outcomes when they are closely monitored and managed appropriately during pregnancy.

Stay tuned with us for more health related topics.

Follow us on LinkedIn and Instagram for more.

Medical Disclaimer!

This article has been reviewed and written under the guidance of our Head Physiotherapist, Dr. Kruti Raj (PT, MUHS,CPT,CMPT). The information shared is intended for educational purposes only and should not be considered a substitute for personalized medical advice, diagnosis, or treatment.

Please consult us or any other qualified healthcare professional before beginning any exercise program, especially if you are experiencing pain, recovering from injury, or managing a medical condition.