When should I have a growth scan?

Growth scans are most commonly performed from 28 weeks onwards, with repeat scans every 2-4 weeks if growth monitoring is required. A single reassurance growth scan can be performed at any point from 24 weeks.

How accurate is the estimated fetal weight?

Ultrasound estimated fetal weight has an accuracy of approximately plus or minus 15% at term. This means the actual birth weight may be somewhat higher or lower than the estimate. Serial measurements over time are more informative than a single measurement.

What does it mean if my baby is measuring small?

A baby measuring below the 10th centile is described as small for gestational age. This does not necessarily mean there is a problem -- some babies are constitutionally small. However, it warrants further assessment including Doppler blood flow studies and closer monitoring.

Do I need a full bladder for a growth scan?

No. Unlike early pregnancy scans, a growth scan in the third trimester does not require a full bladder. Your baby is now large enough to be visualised clearly through the abdominal wall.

Can I find out the sex of my baby at a growth scan?

Sex determination at a growth scan is possible but not always reliable, as your baby is now larger and may be in a position that makes visualisation difficult. If you would like to know the sex, please mention this at the start of your appointment.

How often should I have growth scans?

If growth monitoring is recommended, scans are typically performed every 2-4 weeks. More frequent scanning does not provide additional benefit and can cause unnecessary anxiety. A single reassurance scan is appropriate for low-risk pregnancies.

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Written Report— Within 24 hours

HCPC Registered

CQC Compliant

Same-Day Available

Written Report

Pregnancy Scans

Growth Scan (Third Trimester)

A detailed third trimester assessment measuring your baby's size, checking growth rate, assessing amniotic fluid levels, and evaluating placental function and blood flow.

30-40 minutes

Same-day appointments

Marylebone, London W1

HCPC RegisteredCQC CompliantSame-Day AvailableWritten Report IncludedPregnancy Specialist

£235

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Written report within 24 hours

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Understanding Your Situation

Making Sure Your Baby Is Growing as Expected

In the third trimester, your baby's growth rate becomes one of the most important indicators of their wellbeing. Whether your midwife has noted a measurement concern, you are carrying a baby with a known risk factor, or you simply want the reassurance of knowing your baby is growing well, a growth scan provides detailed, accurate measurements and a comprehensive assessment of your baby's health. Our specialist sonographers will explain every measurement and what it means for your pregnancy. At our Marylebone clinic on Weymouth Street, same-day appointments are available and no GP referral is needed.

Clinical Overview

What is a Growth Scan?

A growth scan is a detailed ultrasound examination performed in the third trimester, typically from 28 weeks onwards, to assess your baby's size and growth rate. The sonographer measures the head circumference, abdominal circumference, and femur length to estimate your baby's weight and plot it on a growth chart. Amniotic fluid volume and placental function are also assessed. Approximately 1 in 10 babies is identified as small for gestational age, making growth monitoring an important part of third trimester care.

Is This Scan Right for You?

Who Should Book This Scan?

Women whose fundal height measurement is smaller or larger than expected for their dates

Patients with a previous small-for-gestational-age or large-for-gestational-age baby

Women with gestational diabetes, pre-eclampsia, or other pregnancy complications

Those with a low-lying placenta or placenta praevia requiring monitoring

Women carrying twins or multiples requiring individual growth assessments

Anyone seeking reassurance about their baby's size and wellbeing in the third trimester

Diagnostic Scope

What This Scan Can Detect

Fetal Growth Restriction

Baby measuring below the 10th centile for gestational age, indicating possible placental insufficiency.

Macrosomia

Baby measuring above the 90th centile, associated with gestational diabetes and delivery planning considerations.

Oligohydramnios

Reduced amniotic fluid volume, which can indicate fetal distress or reduced kidney function.

Polyhydramnios

Excess amniotic fluid, which may be associated with fetal swallowing difficulties or maternal diabetes.

Placental Position

Confirmation of placental location, particularly important for women with a previously noted low-lying placenta.

Umbilical Artery Doppler

Blood flow assessment in the umbilical cord to evaluate placental function and fetal wellbeing.

Your Appointment

What Happens During Your Scan

Arrival and preparation

No special preparation is required. Arrive comfortably and wear loose clothing that allows easy access to your abdomen.

Biometric measurements

The sonographer measures head circumference, abdominal circumference, and femur length to calculate estimated fetal weight.

Growth chart plotting

Measurements are plotted on a customised growth chart to assess whether your baby is growing along their expected centile.

Fluid and placenta assessment

Amniotic fluid volume is measured and placental position and appearance are assessed.

Doppler and report

Umbilical artery Doppler blood flow is assessed where indicated, and a written report with all measurements is provided.

Before Your Appointment

How to Prepare for Your Scan

1
No special preparation is required for a growth scan -- you do not need a full bladder
2
Eat and drink normally before your appointment
3
Wear loose, comfortable clothing that allows easy access to your abdomen
4
Bring your maternity notes and any previous scan reports
5
Allow 40-50 minutes for your appointment including discussion time

After Your Scan

Understanding Your Growth Scan Results

Your sonographer will explain all measurements during the scan and provide a written report before you leave. The report includes your baby's estimated weight, centile position, amniotic fluid index, and placental assessment. If measurements are within the normal range, this provides important reassurance. If growth restriction or other concerns are identified, the report will include clear recommendations for follow-up, which you should share with your midwife or obstetrician promptly.

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