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Find out whether you are expecting a boy or a girl at our Marylebone clinic. The gender ultrasound-scan also checks foetal wellbeing, placental position, and amniotic fluid levels — giving you reassurance alongside the answer you have been waiting for.
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A baby gender ultrasound-scan, also called a baby sexing scan or foetal sex determination scan, uses high-frequency sound waves to visualise the baby's external genitalia. At Sonoworld, the scan is performed transabdominally using a GE Voluson ultrasound machine — the same technology used in NHS fetal medicine units — by a HCPC-registered sonographer with specialist obstetric training.
The NHS does not offer a dedicated gender scan. The 20-week anomaly scan may reveal the sex if the sonographer is able to see clearly, but this is not guaranteed. A private gender ultrasound-scan at Sonoworld gives you a dedicated appointment focused entirely on determining your baby's sex, alongside a mini wellbeing assessment.
If you are expecting twins, the gender scan is priced at £255. Both babies are assessed individually during the same appointment. Please mention your twin pregnancy when booking.
Foetal sex is determined by visualising the external genitalia using the angle of the genital tubercle (the nub theory), the presence of the scrotum and penis in male foetuses, or the three-line sign (labia majora and clitoris) in female foetuses. The reliability of these markers increases significantly after 16 weeks of gestation.
| Marker | Male | Female |
|---|---|---|
| Genital tubercle angle | >30° from horizontal | <10° from horizontal |
| Scrotal / labial folds | Scrotum visible | Labia majora visible |
| Penile shaft | Visible after 16 weeks | Absent |
| Three-line sign | Absent | Present (clitoris + labia) |
| Reliability at 16 wks | ~95% | ~97% |
| Reliability at 18+ wks | >99% | >99% |
If the baby's position makes it impossible to confirm the sex during the appointment, the sonographer will ask you to walk around for a few minutes to encourage the baby to move. In the rare event that a clear view cannot be obtained, Sonoworld will offer a complimentary rescan at no additional charge.
Gender scan is not a diagnostic scan
The gender ultrasound-scan is a wellbeing and sex-determination scan. It does not replace the 20-week anomaly scan, which screens for structural abnormalities. If you have not yet had your NHS anomaly scan, Sonoworld recommends booking a growth scan alongside your gender scan for more comprehensive assessment.
The gender ultrasound-scan can be performed from 16 weeks of pregnancy. Accuracy improves with gestational age — the optimal window is between 16 and 24 weeks, when the baby is large enough for clear visualisation but still has sufficient room to move into a good position.
Gender can usually be confirmed at 16 weeks, with accuracy around 95%. The genitalia are clearly forming but smaller, so baby position is more important at this stage.
The most reliable time for gender determination. Accuracy exceeds 99%. The baby is large enough for clear images and still has good mobility in the womb.
Gender determination remains highly accurate in this period. The baby is larger, which can occasionally make positioning more challenging, but the genitalia are clearly developed.
Gender can still be confirmed after 28 weeks, though the baby's engaged position may occasionally limit the view. A growth scan is often more clinically useful at this stage.
Drink 1 litre (approximately 2 pints) of water one hour before your appointment. A full bladder lifts the uterus and provides a clearer acoustic window for the ultrasound-scan, particularly in the second trimester.
You do not need to fast before a gender ultrasound-scan. Eating a light meal beforehand may actually encourage the baby to be more active, which can help with positioning.
Wear loose, comfortable clothing that allows easy access to your lower abdomen. A two-piece outfit (top and trousers or skirt) is ideal. You will be asked to lower your waistband slightly during the scan.
The appointment takes approximately 20 minutes from start to finish. Here is what to expect at each stage.
The sonographer takes a brief obstetric history, confirms your gestational age, and explains the procedure. You sign a consent form before the scan begins.
You lie on the examination couch and expose your lower abdomen. Warm ultrasound gel is applied and the probe is moved gently across the skin to obtain images of the baby.
The sonographer checks the foetal heartbeat, movement, placental position, and amniotic fluid levels before focusing on gender determination.
The sonographer identifies the genital area and confirms the sex. If the baby is not in an optimal position, you may be asked to walk briefly to encourage movement before a second attempt.
You receive a 2D ultrasound image and a written report confirming the findings. The report is available on the same day and can be shared with your midwife or GP.
Choose your preferred date and time below. Booking is confirmed immediately. No GP referral is required.
Price includes the scan, verbal feedback, 2D image, and written report. Insurance patients: please bring your authorisation code.
Please mention your twin pregnancy when booking so the sonographer can allocate sufficient appointment time.
Insurance patients are seen at the same price. Please bring your authorisation code. Sonoworld is recognised by most major UK health insurers.
Confirms viability, heartbeat, and gestational age in the first trimester.
£235
Measures foetal growth, checks blood flow, and assesses wellbeing in the third trimester.
£235
Confirms baby's position (head-down, breech, or transverse) ahead of delivery.
£235
At 16 weeks, accuracy is approximately 95% for male foetuses and 97% for female foetuses. From 18 weeks onwards, accuracy exceeds 99% in both cases. The primary factor affecting accuracy is the baby's position during the scan. If a clear view cannot be obtained, Sonoworld will offer a complimentary rescan.
Sonoworld does not offer gender scans before 16 weeks. Before this point, the external genitalia are not sufficiently developed for reliable determination, and the risk of an incorrect result is too high. The earliest reliable appointment is at 16 weeks and 0 days.
Yes. You should drink 1 litre (approximately 2 pints) of water one hour before your appointment and avoid emptying your bladder before the scan. A full bladder pushes the uterus upward and provides a clearer acoustic window for the transabdominal ultrasound-scan.
Yes. You are welcome to bring one guest to share the experience. The consultation room accommodates the patient and one accompanying person comfortably. Please let us know at the time of booking if you plan to bring a guest.
If the baby's position prevents a clear view of the genitalia, the sonographer will ask you to walk around for a few minutes to encourage movement. In the rare event that gender cannot be confirmed during the appointment, Sonoworld will arrange a complimentary rescan at no additional cost.
No. The gender scan is a focused wellbeing and sex-determination scan. The NHS 20-week anomaly scan is a detailed structural survey that screens for over 11 conditions, including heart defects, spina bifida, and cleft lip. The gender scan does not replace the anomaly scan and should be booked in addition to your NHS appointments.
Appointments can be cancelled or rescheduled free of charge with at least 24 hours' notice. Cancellations made with less than 24 hours' notice may incur a cancellation fee. To reschedule, call 020 3633 4902 or email info@sonoworld.co.uk.
Located in the heart of London's medical district, a short walk from Regent's Park and Great Portland Street Underground stations.
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