What is the anomaly scan, and when does it happen?
In short
- The anomaly scan is a detailed ultrasound. It checks your baby's body, organs and growth.
- It's usually done at 18 to 21 weeks (up to 23 if needed), or 18 to 22 weeks in US guidance.
- It checks for a specific list of conditions, not everything that could go wrong.
- Your sonographer explains what was checked. Your doctor discusses any findings with you.
What happens
- A sonographer applies gel to your abdomen and moves a scanner over it, usually for 20 to 45 minutes.
- They measure your baby's body parts and organs and check them against a checklist of specific conditions.
- If everything looks as expected, you're usually told so at the time; anything that needs a closer look is explained and followed up.
Baby's sex is never revealed
It is illegal in India for anyone -- including your sonographer -- to reveal, or help you find out, the sex of your baby before birth. This is the Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994.
Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994. Read the Act (India Code).
The details: numbers and where they differ
In the source's own words
The 20-week screening scan, also called the anomaly scan, is an ultrasound scan to look for 11 different conditions in your baby. It also checks your baby's growth. It's usually done when you're between 18 and 21 weeks pregnant.
NHS (UK), 20-week scan. Quoted verbatim.
The numbers
| Measure | Value | Source |
|---|---|---|
| Anomaly scan window (pregnant women) | 18–21 (NHS) / 18–22 (ACOG) weeks gestation | NHS (UK) |
| Latest usual anomaly scan (NHS, exceptional cases) (pregnant women, UK, when the scan is delayed) | up to 23 weeks gestation | NHS (UK) |
When to call your doctor
- If you haven't been offered this scan and aren't sure when yours is scheduled.
- If your sonographer or doctor flags anything that needs a follow-up scan or appointment.
Discuss your results with your doctor: this page reports what these sources say, not advice for your situation.
Sources
- NHS (UK), 20-week scan. Quoted verbatim. OGL-style NHS content, free reuse with attribution.
- American College of Obstetricians and Gynecologists (ACOG), Ultrasound Exams (Patient FAQ). Named as the guideline this section describes; its text and tables are not reproduced here (All rights reserved (cite only)). Names 18 to 22 weeks as the usual timing for the one standard ultrasound exam of pregnancy.
Sources checked 2026-09-26. How we source and check every page.
Educational summary of named sources, not medical advice.