What to know about a 33-week growth scan

The sonographer measures parts of the baby's head, abdomen and thigh bone. The ultrasound software uses these measurements to estimate fetal weight. Your care team interprets the estimate alongside earlier scans, your health and the course of the pregnancy.

A single estimated weight is not a precise weighing of the baby. The pattern across time is often more informative than one measurement, because ultrasound estimates have a margin of variation. The scan may also document whether the baby is head-down or breech, the amount of amniotic fluid and where the placenta lies.

If growth appears smaller or larger than expected, your clinician may review pregnancy dates, repeat the scan, assess blood flow through the umbilical cord or discuss additional monitoring. A finding outside the expected range does not by itself establish a problem.

Follow the imaging centre's instructions about eating, drinking and bladder preparation, as local protocols differ. Bring prior scan reports and your maternity notes if they are not already available electronically. Wear clothing that makes the abdomen easy to uncover.

Afterward, confirm who will explain the report and whether another appointment is planned. Continue normal antenatal care and pay attention to your baby's usual movement pattern; a reassuring scan does not replace reporting a noticeable reduction or change in movements.

Contact your maternity unit promptly if your baby is moving less than usual or the movement pattern changes. Seek urgent assessment for vaginal bleeding, leaking fluid, regular painful tightenings, severe abdominal pain, severe headache with visual disturbance, or sudden swelling with feeling unwell. Do not wait for a scheduled ultrasound when these symptoms occur.

Ask how the estimated size compares with earlier measurements, whether the fluid and placenta look as expected, and whether the baby's position matters at this stage. If follow-up is advised, ask what will be monitored, when it should happen and which symptoms should lead you to call sooner.