What should you know about a 38-week growth scan?

The sonographer measures the baby's head, abdomen and thigh bone, then uses those measurements to calculate an estimated weight. The scan may also assess the placenta, the baby's position and blood flow through the umbilical cord when clinically indicated.

A single ultrasound provides an estimate rather than an exact birth weight. Your clinician interprets it alongside earlier measurements, your baby's growth pattern, fluid level, blood-flow findings and your health. A measurement above or below the expected range does not by itself diagnose a problem.

If growth appears slower than expected, fluid is low or a blood-flow check is concerning, the team may recommend closer monitoring or discuss the timing of birth. If the baby appears larger than expected, they will consider the full clinical picture before discussing birth options.

Follow the clinic's instructions about eating, drinking and bringing your maternity records, as local arrangements differ. Wear clothing that makes your abdomen easy to access. Tell the sonographer about changes in movement, pain, bleeding, fluid leakage or contractions rather than waiting until the scan ends.

Afterward, ask how the estimated size compares with previous measurements and whether the result changes your monitoring or birth plan. Depending on the findings, the next step may be routine antenatal care, another assessment, fetal heart-rate monitoring or a discussion about induction or caesarean birth.

Contact your maternity unit immediately if your baby's movements are reduced, have stopped or have changed from the usual pattern. Do not wait for a booked scan or use a home heartbeat device for reassurance.

Urgent assessment is also needed for vaginal bleeding, suspected waters breaking, severe or persistent abdominal pain, a severe headache with visual disturbance, sudden marked swelling, chest pain, breathing difficulty, a seizure or feeling seriously unwell. Call local emergency services for a life-threatening emergency.

Ask which measurements were taken, whether growth has followed the expected pattern and whether the fluid or blood-flow findings need follow-up. You can also ask how measurement uncertainty affects the interpretation, whether monitoring is recommended and what findings would change the planned timing or method of birth.