Pregnant women are often confused by the different types of ultrasound scans. The anatomy scan and growth scans serve completely different purposes — here's what each one checks and when you need them.
The Anatomy Scan: 18–22 Weeks
The anatomy scan is a detailed structural survey of your baby. It checks whether organs and body parts have formed normally. It is done once, at a specific window when the baby is large enough to visualise but still in the right position for measurement.
| What Anatomy Scan Checks | Details |
|---|---|
| Brain and skull | Shape, ventricle size, cerebellum |
| Face | Lip, palate, nose bone (markers for chromosomal risk) |
| Heart | Four chambers, outflow vessels, rhythm |
| Spine | Full vertebral column for neural tube defects |
| Organs | Kidneys, stomach, bladder, abdominal wall |
| Limbs | Arms, legs, hands, feet count |
| Placenta and fluid | Position, amniotic fluid index |
Growth Scans: From 28–34 Weeks Onward
Growth scans do not look at structure — they measure size. The sonographer records head circumference, abdominal circumference, femur length, and estimates the fetal weight. These measurements are plotted on a growth chart to check whether the baby is growing at the expected rate.
| What Growth Scans Check | Details |
|---|---|
| Biometry measurements | HC, AC, FL, estimated weight |
| Growth percentile | Compared to gestational age norms |
| Amniotic fluid index | Reflecting kidney function and wellbeing |
| Doppler blood flow | Umbilical artery, middle cerebral artery |
| Placenta | Appearance changes with age — grading |
When Are Extra Growth Scans Ordered?
- Small or large for gestational age on previous scan
- Maternal high blood pressure or pre-eclampsia
- Gestational diabetes
- Twin pregnancy (routine growth scans throughout)
- Previous pregnancy with IUGR or stillbirth
- Abnormal Doppler on a previous scan
Note
If you are having a normal, uncomplicated singleton pregnancy, you may not have a growth scan at all after the anatomy scan. That is normal and not a sign that your baby is being ignored.