Understanding a 31-week growth scan

It provides a snapshot that is interpreted with your due date, earlier measurements and reason for referral. The appointment may be planned because of your medical history, a clinical concern or the maternity service's care pathway.

The sonographer usually measures the head, abdominal area and thigh bone. Those values help calculate an estimated fetal size. Fluid around the baby is assessed, and the scan can show whether the baby is head-down, bottom-down or lying across the uterus at that moment.

Small differences can arise from fetal position and the limits of ultrasound estimation. Clinicians look for a coherent growth pattern and decide whether a repeat scan or closer monitoring would add useful information. Position at 31 weeks can still change before labour.

Check the instructions in your appointment message, including whether you need any bladder preparation. Choose comfortable separates, take your maternity record if requested and note any questions about movements, symptoms or earlier results.

You will normally lie back while the sonographer applies gel and moves a handheld probe across your abdomen. You may be asked to shift position so different views can be obtained. Make sure you know who will explain the report and whether another appointment is needed.

Call your maternity unit promptly if fetal movements become less frequent, weaker or noticeably different for your baby. A growth-scan booking is not a substitute for a movement assessment.

Urgent advice is also needed for bleeding, suspected waters breaking, persistent severe abdominal pain, regular painful contractions, or a severe headache accompanied by blurred vision or sudden swelling. Follow the emergency instructions given by your maternity team.

Ask how today's measurements compare with previous ones, whether the fluid and placenta findings require follow-up, and what changes in movement should trigger a call. If another scan is planned, ask what decision its results will help the team make.