First dating scan in pregnancy: what to expect

The sonographer uses ultrasound to look at the uterus and pregnancy. The scan may help confirm the pregnancy location, assess whether development matches the expected stage, and estimate the due date from measurements. Depending on how early the pregnancy is, the scan may be performed through the abdomen or with a vaginal probe. A very early scan can be inconclusive if the pregnancy is not yet visible clearly, so repeat imaging or blood tests may be discussed.

The date calculated by ultrasound is an estimate used for care planning. It may differ from a date based only on the last menstrual period, especially when cycles are irregular or ovulation occurred later than expected.

Follow the appointment instructions about drinking water and arrive with details of your last menstrual period, cycle pattern, fertility treatment if relevant, and any bleeding or pain. Wear clothing that allows access to the abdomen. You can ask what the scan can and cannot show, when results will be discussed, and whether a later screening scan is planned.

A dating scan is not an emergency assessment. Contact your maternity team urgently for heavy bleeding, severe or one-sided abdominal pain, shoulder-tip pain, dizziness, fainting, or feeling very unwell. If the scan cannot confirm expected development, ask what follow-up is planned and when to return. Do not interpret an uncertain early scan without the clinician's explanation.

Ask what was seen, how the estimated due date was calculated, whether the pregnancy is in the uterus, and whether another scan is needed. Ask how the dating scan differs from a nuchal translucency scan and which appointment comes next.