Gender scan: finding out your baby's sex on the NHS and privately

A gender scan is an ultrasound examination in which the baby's genitalia are looked at to give an opinion on whether the baby is male or female. On the NHS this is not a separate scan: it is offered as an add-on if you ask during the 20-week screening scan, which is also called the anomaly scan.

The NHS explains that the 20-week scan is an ultrasound scan to look for 11 different conditions in your baby and to check growth, and it is usually done when you are between 18 and 21 weeks pregnant. Its purpose is health screening, not sex determination, which is why it is treated differently from the checks themselves.

An NHS Scotland guideline, approved by an obstetric clinical governance group, sets out the approach. It says there is no requirement to determine fetal sex in the screening programme; however disclosure on request respects a woman's autonomy over personal health information. If the sonographer can determine the sex with certainty and the patient wishes to know, they should say so and document it in the report.

The guideline says the sonographer should establish at the start of the examination whether the patient wishes to know, obtain verbal consent, and advise that it is not always possible to determine the sex, that it is not always 100% accurate and that the examination will not be extended to determine it. There are also occasions where a woman does not want to know but medical staff need the information for future management; in that case it is recorded in the report with a note that the patient does not wish to be told.

The NHS page itself says that you may be asked if you would like to know the sex of your baby. University Hospitals Sussex says checking the sex is not part of the health checks, so it will only be done if you ask the sonographer. Local practice differs, so ask your own unit what its policy is.

The sonographer gives an opinion. University Hospitals Sussex says this is not 100% accurate. The NHS Scotland guideline describes how it is done: the genitalia should be seen directly in several views, with male sex determined by clear visualisation of the penis and scrotum and female sex by identification of the parallel lines representing the labia, and an image is kept in the notes.

If the genitalia cannot be clearly seen within the time available, the guideline says the examination should not be prolonged or repeated, and the sonographer should document that the sex could not be determined. That is a common reason people leave an NHS scan without an answer: the baby may be curled up, have legs crossed, or be in a position that does not allow a clear view.

The NHS says the scan is usually done at a local hospital, clinic or health centre by a trained healthcare professional, takes around 30 minutes, and may take longer if the baby is moving or not in the right position. You may be asked to go for a walk or eat something and come back after a break. If clear pictures are still difficult, you are offered another appointment before you are 23 weeks pregnant.

You lie on a couch in a dimly lit room, with a cold gel on your tummy, and a probe is moved over it. The sonographer checks bones, heart, brain, spinal cord, face, kidneys and tummy, and the placenta and blood flow in the uterus. You may need a full bladder, and you should bring maternity notes. The NHS notes that you may need to pay for pictures of your baby, so check with the clinic.

The NHS lists practical steps: arrive early, wear loose clothing, take out a belly piercing, bring maternity notes if you have paper notes, and have a full bladder if you have been told to. It says you can bring someone to the scan but most hospitals do not allow children.

If you want to know the sex, say so at the start. If you do not want to know, say that too, and tell anyone coming with you. Because the sonographer may not be able to see, it is sensible not to plan a gender reveal around the NHS scan.

The NHS Scotland guideline says the sex information should not be shared with the patient's friends or relatives, and says that the slip handed to the patient is not given in an envelope. It also lists a Society and College of Radiographers publication on the sale of images, determination of fetal gender and commercial aspects related to NHS obstetric ultrasound as a reference, which shows that commercial scanning is regarded as a separate area from the NHS service.

Private ultrasound services outside the NHS offer scans where the sex is the main purpose. The sources reviewed here do not describe those services, so the practical points are general: check who performs the scan and what training and registration they have, what the scan can and cannot tell you, and that it does not replace the NHS screening scan.

The NHS says most people are told their baby does not have signs of a condition. If the scan finds something, you may be offered further scans and tests, such as amniocentesis or chorionic villus sampling, and referred to a specialist. It also notes that the scan cannot find all conditions and that you should tell your midwife about any symptoms or concerns. Antenatal Results and Choices (ARC) offers information and a helpline for people told their baby may have a condition.

The scan is optional. The NHS says it is your choice whether to have it, and if you decide not to and change your mind later you should speak to your midwife or GP.

The NHS 20-week scan is offered free to everyone and prioritises screening. Whether the sex is disclosed depends on local policy, the baby's position and the sonographer's confidence. Scans bought outside the NHS are a separate service with a different purpose. The sources reviewed here do not describe them, so ask any provider about the sonographer's qualifications, what the scan can and cannot show, and that it does not replace NHS screening.