Growth Scan: Complete Guide

A growth scan is an extra ultrasound offered later in pregnancy to check how well your baby is developing, beyond the routine measurements your midwife takes at appointments. Most pregnancies never need one, but if you've been offered one, it helps to know what to expect and why it's been recommended.

Why Growth Scans Are Offered

Growth scans are not routine for every pregnancy — they're offered when there's a specific reason to check more closely.

Your baby measuring smaller or larger than expected on symphysis-fundal height (the tape measure check at antenatal appointments) is one of the most common reasons for referral.
Pre-existing or gestational diabetes, since this can affect how large a baby grows.
High blood pressure or pre-eclampsia, which can sometimes restrict how well the placenta supports growth.
A history of a small or large baby, or other complications, in a previous pregnancy.
Reduced fetal movements reported at any point, or concerns raised at a routine appointment.
Carrying twins or a multiple pregnancy, where growth scans are typically scheduled routinely through the third trimester.

What Happens During the Scan

A growth scan uses the same ultrasound technology as your earlier scans, though the focus and measurements differ.

The sonographer measures your baby's head circumference, abdominal circumference, and femur (thigh bone) length, then uses these to estimate weight.
They also check the amount of amniotic fluid around your baby, since too much or too little can be worth monitoring.
Doppler measurements of blood flow through the umbilical cord are sometimes taken too, particularly if placental function is a concern.
The appointment usually takes around 20-30 minutes, and you can normally see the screen throughout, though the sonographer's focus is on accurate measurements rather than commentary.
Results are plotted on a growth chart and compared against previous scans to track the trend over time, not just a single measurement.

Understanding Your Results

A single growth scan is a snapshot, and estimated fetal weight carries a margin of error, so try not to fixate on one number alone.

Your care team looks at the overall pattern across scans rather than one reading — a baby consistently tracking its own growth curve is usually healthy even if that curve sits below or above average.
If a concern is identified, you'll usually be offered a follow-up scan a couple of weeks later, along with closer monitoring.
On the NHS, growth scans are free when medically indicated. Privately, one typically costs £60-£150, though this varies by clinic and region.

Frequently Asked Questions

Will I automatically be offered a growth scan?

No, most pregnancies don't need one. Your midwife checks your baby's growth using a tape measure (symphysis-fundal height) at each antenatal appointment, and a growth scan is only arranged if there's a specific concern, such as measuring outside the expected range, diabetes, or relevant history from a previous pregnancy.

What does a growth scan actually check?

It measures your baby's head, abdomen, and thigh bone to estimate weight, checks amniotic fluid levels, and sometimes measures blood flow through the umbilical cord. Results are plotted on a growth chart and compared with earlier scans to see the overall trend.

Is a small or large measurement on a growth scan something to worry about?

Not necessarily on its own. Estimated fetal weight has a margin of error, so your care team focuses on whether your baby is following a consistent growth curve across scans rather than a single measurement. If there's a genuine concern, you'll usually be offered closer monitoring or a follow-up scan.

This article is for informational purposes only and does not constitute medical advice.

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