What to know about a 30-week growth scan

The sonographer combines several measurements rather than judging growth from a single image. Your maternity clinician interprets the findings alongside earlier scans, your pregnancy history and any current concerns.

Measurements commonly include the baby's head, abdomen and thigh bone. The ultrasound software uses these to estimate fetal size, while the examination also records the baby's position and assesses amniotic fluid. The placenta can be viewed for its location and general appearance.

An estimate is not an exact birth weight. A pattern across scans is often more informative than one measurement, so an unexpected result may lead to another ultrasound or additional checks rather than an immediate conclusion.

Follow the clinic's instructions about eating, drinking and bladder preparation because local protocols vary. Wear clothing that makes your abdomen easy to uncover, and bring relevant maternity notes or previous scan reports if they are not already available electronically.

During the scan, gel is placed on your abdomen and a probe is moved over the skin. The baby's position can affect how quickly clear measurements are obtained. Ask when and how the results will be discussed before leaving.

Do not wait for a scheduled scan if your baby's movements are reduced or have changed from their usual pattern. Contact your maternity unit promptly for advice and assessment.

Seek urgent maternity care for vaginal bleeding, leaking fluid, regular painful tightenings, severe abdominal pain, a severe headache with vision changes, or sudden marked swelling. These symptoms need assessment regardless of a recent reassuring ultrasound.

You might ask whether growth is following the expected pattern, where the placenta is located, how the fluid assessment looks and whether your baby's position matters at this stage. If follow-up is advised, clarify what will be checked and when you should return.