How does a growth scan work?

During the scan, a sonographer moves a probe over your abdomen using gel to create images. Measurements commonly include the baby's head, abdomen and thigh bone. These are compared with earlier scans or a growth pattern expected for the stage of pregnancy; one measurement alone does not explain the whole picture.

The scan can also assess the baby's position, movement, heartbeat, amniotic fluid and placenta. Doppler ultrasound may examine blood flow through vessels in the umbilical cord or uterus when growth, placental function or another pregnancy feature needs closer assessment. A result may lead to monitoring, another scan or a discussion about timing and place of birth.

Wear clothing that allows access to your abdomen and bring previous scan information if requested. You can usually eat and drink normally unless your maternity team gives different instructions. Ask when the report will be discussed and what follow-up is planned if measurements, fluid or blood flow need checking again.

A scan appointment should not replace urgent assessment. Contact your maternity unit promptly for reduced or changed fetal movements, vaginal bleeding, leaking fluid, regular painful contractions, severe abdominal pain, severe headache or vision changes. Use the urgent route recommended for your pregnancy rather than waiting for a scheduled scan.

Ask which measurements will be taken, whether Doppler blood-flow assessment is planned, how your baby's growth compares with earlier findings, and what the next step would be if the result needs review.