Why is 3D/4D ultrasound used in a growth scan?

A growth scan commonly uses measurements of the baby's head, abdomen and thigh bone, together with assessment of fluid, placenta and sometimes blood flow. Three-dimensional imaging can create a more complete view of a selected area, while four-dimensional imaging shows movement. This may help when the baby's position makes a body surface or organ difficult to see, or when the team wants to review a particular feature. The technology does not measure growth from appearance alone. Trends in measurements, pregnancy dates and Doppler findings, when required, are considered together.

Use the preparation instructions given by your maternity unit and allow enough time for the examination. Ask whether the scan is focused on growth, fluid, placental position or blood flow. If the sonographer cannot obtain a reliable view, a repeat appointment may be suggested. Keep any follow-up appointment so your clinician can compare measurements over time and explain whether the findings need monitoring.

A request for extra imaging does not automatically mean that growth is abnormal. Seek urgent maternity advice for reduced fetal movement, vaginal bleeding, leaking fluid, severe pain, severe headache with visual changes or sudden swelling. These concerns should be assessed directly rather than judged from an ultrasound image.

Ask which measurements were obtained, whether they follow the expected pattern for your pregnancy dates, whether blood-flow assessment was needed, and when the next growth review should take place.