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✅ No Fasting Needed ⏱ 30–45 minutes

👶 How to Prepare for a
Pregnancy Anomaly Scan (20-Week Scan)

The anomaly scan, performed between 18 and 22 weeks of pregnancy, is the most detailed ultrasound of your baby's development. It checks the baby's brain, heart, spine, kidneys, limbs, and facial features, and gives an accurate assessment of growth, position, and placental location.

✅ Preparation Steps

1
Have a moderately full bladder
Unlike early pregnancy scans, the 20-week scan is usually done through the abdomen — a full (but not painfully distended) bladder helps. Drink 2–3 glasses of water about 45–60 minutes before your appointment, and do not urinate. If your bladder becomes uncomfortably full, you may partially empty it on arrival.
2
Eat and drink normally — no fasting required
No dietary restrictions apply. Some women find that eating a light meal 30–60 minutes before the scan makes the baby more active, which can help if certain views are difficult to obtain. Heavy or greasy meals are not recommended as they can cause discomfort lying flat.
3
Wear loose, two-piece clothing
The scan requires access to the lower abdomen. Loose trousers or a skirt with a separate top are most practical. Avoid a tight one-piece dress or bodysuit that restricts access.
4
Bring your pregnancy handheld record (maternity card)
Your maternity card contains your previous scan reports, blood results, and clinical history — all essential for the sonographer to interpret the current scan in context, particularly if any previous concerns were noted.
5
Plan for the full appointment time
The anomaly scan takes 30–45 minutes on average, but can take longer if the baby is in an awkward position. Some views (especially the cardiac outflow tracts and face) require patience while waiting for the baby to move. Do not book the scan on a day when you are in a rush — and plan for the possibility that you may need to walk around or return in 20–30 minutes if the baby needs to change position.
6
Bring your partner or a support person
This scan is often an emotional and memorable experience — the first detailed look at your baby. Partners and family members are welcome at Mascot Healthcare. Some parents bring a phone or camera for video/photos of the screen.

🎒 What to Bring

🔬 What to Expect

Positioning and gel application
You will lie on the scan couch and your abdomen will be exposed from the waist to just above the pubic hairline. Warm ultrasound gel is applied — it is water-based and wipes off cleanly afterwards.
Systematic scan (25–40 min)
The sonographer works through a standardised checklist: head (brain, ventricles, cerebellum, nuchal fold), face (lips, nose, eyes), spine, heart (4-chamber view and outflow tracts), abdominal wall (umbilical cord insertion), kidneys, bladder, limbs (long bones, hands, feet), placenta location, amniotic fluid volume, and umbilical Doppler. Each structure is measured and documented.
Baby's sex (if requested)
If you want to know the baby's sex, tell the sonographer at the start. Sex can usually be determined at 20 weeks, though it depends on baby's position. If you do not want to know, confirm this clearly so it is not mentioned inadvertently.
Reporting
A written report is prepared and handed to you at the end of the appointment, or sent to your obstetrician. If any concern is noted, the sonographer will explain it at the time and advise on next steps (e.g., fetal echocardiogram referral for heart concerns, repeat scan in 4 weeks for a low-lying placenta).

🏠 After Your Test

Frequently Asked Questions

What happens if the anomaly scan finds a problem?
Finding an anomaly does not automatically mean a serious outcome — many findings are minor, common, or resolve on their own (e.g., mild hydronephrosis, echogenic bowel, choroid plexus cysts). If a significant finding is detected, you will be referred promptly to a fetal medicine specialist or paediatric cardiologist for a detailed assessment. You will not be left without guidance — the sonographer and your obstetrician will explain what was found and what it means in clear, calm terms.
Is 18 weeks too early or too late for the anomaly scan?
The optimal window is 18–22 weeks. Before 18 weeks, some structures (particularly the heart outflow tracts) may not be fully formed enough for accurate assessment. After 24 weeks, the baby is larger and harder to image fully. If you are outside this window due to late booking, the scan should still be done — partial information is better than none.
Can the anomaly scan miss abnormalities?
No ultrasound scan can guarantee a 100% perfect baby. The anomaly scan is designed to detect major structural abnormalities and has good sensitivity for serious conditions. However, some conditions (mild heart defects, chromosomal abnormalities, autism, intellectual disability) cannot be detected by ultrasound alone. The scan is a screening tool — not a guarantee.
My baby didn't cooperate — what happens now?
If the baby is in a position that prevents complete scanning (e.g., hiding the face or heart), you will be asked to walk around or empty your bladder to encourage movement. If the scan remains incomplete, a repeat appointment is booked — usually within 2–4 weeks. An incomplete anomaly scan is not a cause for alarm; it simply means the baby was in an unhelpful position on the day.

Related Pages

Anomaly Scan StoryConfirm Pregnancy Scan StoryDoppler BPP Scan Story

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