Growth Scan in Pregnancy: Why Doctors Recommend It

About the Author (Dr Asha R. Rao, MD (OBG), Fertility Specialist)

Dr Asha R. Rao is a senior obstetrician and gynaecologist with extensive experience in high-risk pregnancies, fertility care, and women's health. She is dedicated to providing evidence-based, compassionate maternity care. & Dr Suganya B. is a consultant obstetrician and gynaecologist specialising in prenatal care, maternal wellness, and comprehensive pregnancy management. She is committed to delivering personalised, evidence-based care for mothers at every stage of pregnancy.

In this article, we will discuss: 

1. Checks fetal growth and wellbeing
2. Measures fetal biometry and weight
3. Assesses fluid and placental blood flow
4. Helps identify fetal growth restriction
5. Guides monitoring and delivery planning

A growth scan can feel worrying when your doctor recommends one, especially if earlier scans were normal. In most cases, it is simply a way to get more information about how your baby is growing and whether the pregnancy needs closer monitoring.

The key is understanding that one measurement does not tell the whole story. Growth over time, amniotic fluid, Doppler findings and your clinical history are interpreted together.

What is a growth scan?

A growth scan in pregnancy is an ultrasound, usually performed later in pregnancy, that assesses your baby's size and growth pattern along with markers such as amniotic fluid and, when indicated, blood flow. It is different from the detailed anatomy or anomaly scan performed earlier in pregnancy.

What parents should know

A growth scan is not simply a check of the baby's weight. It combines measurements and other findings to help your healthcare team understand whether growth is progressing as expected.

The timing varies. There is no single week that applies to every pregnancy. Your doctor may recommend one because of a risk factor, a concern about growth, or findings from an earlier examination.

What does fetal biometry measure?

Fetal biometry refers to measurements used to assess fetal size and estimate weight. Common measurements include:

These measurements can be combined to calculate estimated fetal weight (EFW) and plotted against an appropriate growth chart. Importantly, fetal size at one point is not the same as growth. Growth is a dynamic process and is better assessed through measurements taken over time. 

When is a growth scan recommended?

A doctor may recommend a third trimester scan when there is increased concern about fetal growth or wellbeing. Reasons can include:

• High blood pressure or pre-eclampsia
• Diabetes during pregnancy
• Previous pregnancy affected by poor fetal growth
• Twins or another multiple pregnancy
• Baby measuring smaller than expected
• Fundal-height measurements suggesting growth may need checking
• Reduced fetal movements
• Other maternal or pregnancy-related risk factors

The exact schedule should be individualised rather than based on a fixed number of scans.

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What does fetal growth restriction mean?

Fetal growth restriction (FGR) means a fetus is not reaching its expected growth potential. A baby measuring small does not automatically have FGR.

A baby may be constitutionally small and otherwise healthy. Conversely, a baby whose measurements are within a seemingly acceptable range may still need assessment if growth has slowed or Doppler findings are concerning. This is why clinicians consider growth trajectory, fetal measurements and placental blood flow together. 

Expert answer

Dr Rijo Mathew Choorakuttil, MD, a clinical radiologist and fetal-radiology specialist involved with India's IRIA Samrakshan programme, has emphasised integrating fetal Doppler assessment with trimester-specific antenatal scans as part of fetal surveillance in India. 

How are growth scan results interpreted?

A percentile or centile is a comparison with babies at the same gestational age. Being at the 25th centile, for example, does not mean something is wrong.

A measurement below the 10th centile can indicate that a baby is small for gestational age (SGA), but it does not by itself establish FGR. Doctors may look at:

• Whether growth is continuing over serial scans
• Abdominal circumference and estimated fetal weight
• Umbilical artery Doppler
• Other Doppler measurements when clinically indicated
• Amniotic fluid
• Maternal blood pressure and medical history

Why does Doppler matter?

Doppler ultrasound assesses blood flow in vessels such as the umbilical artery. When FGR is suspected, these measurements can provide information about placental function and fetal adaptation. Depending on the clinical situation, doctors may also assess cerebral or venous blood flow. 

What happens during the scan?

A growth scan is generally performed using an abdominal ultrasound probe. The sonographer takes the required measurements, assesses fluid and may perform Doppler studies if indicated.

The scan is non-invasive and uses ultrasound rather than radiation. Bring previous scan reports if available, because comparing findings over time can help your doctor assess growth more meaningfully.

Parent checklist

☐ Know why your doctor has recommended the scan
☐ Carry previous ultrasound reports
☐ Ask which measurements were taken
☐ Ask whether growth is tracking appropriately
☐ Understand any percentile or Doppler finding
☐ Follow the recommended follow-up schedule
☐ Report reduced fetal movements promptly rather than waiting for a scheduled scan

What is the practical next step?

Problem: A single growth-scan number can be difficult to interpret.

Solution: Ask your obstetrician to explain the measurements alongside the growth trend, fluid level, Doppler findings and your pregnancy history.

Why it helps: This gives you a clearer picture of whether your baby is growing as expected or needs closer monitoring.

Key takeaways

1. A growth scan assesses more than fetal weight.
2. Fetal growth is best understood over time.
3. Percentiles and Doppler findings need clinical context.

FAQs

Is a growth scan in pregnancy safe?

Diagnostic ultrasound does not use ionising radiation and is widely used in pregnancy. It should be performed by appropriately trained professionals for a clinical purpose. 

Is a baby below the 10th percentile always growth restricted?

No. A baby can be constitutionally small and healthy. FGR is assessed using size together with growth pattern, Doppler findings and other clinical factors. 

How many growth scans are needed?

There is no universal number. The frequency depends on your pregnancy risk factors, previous findings and whether additional monitoring is required.

Can a growth scan predict exactly how much my baby will weigh?

No. Estimated fetal weight is an ultrasound-based estimate rather than an exact measurement. Your doctor interprets it alongside other findings.

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