Anomaly Scan at 20 Weeks: Complete Guide for UK Parents

The 20-week anomaly scan is one of the most detailed and important ultrasounds of your pregnancy. Offered routinely on the NHS, it checks your baby physical development and can detect structural conditions. This guide covers what to expect.

What Is the 20-Week Anomaly Scan?

The anomaly scan is a detailed ultrasound performed between 18 and 21 weeks. Its primary purpose is to check your baby physical development and look for structural abnormalities.

It is offered to all pregnant women on the NHS. The scan is not designed to determine sex, though the sonographer may tell you if the baby is well positioned and you ask.

What the Sonographer Checks

The sonographer examines the brain, face, spine, heart, lungs, stomach, kidneys, bladder, and limbs. They also measure head circumference, abdominal circumference, and femur length.

They check the placenta position, amniotic fluid, and umbilical blood flow. If the placenta is low, a follow-up scan checks whether it has moved.

Preparing and Understanding Results

The scan is transabdominal, so you usually do not need a full bladder. Wear loose clothing and bring your pregnancy notes. The scan takes 30 to 45 minutes.

Most scans show normal development. If anything unusual is found, you may be referred to a specialist. Many findings are minor or resolve on their own.

Can You Find Out the Sex at 20 Weeks?

At 20 weeks, the sonographer can often determine whether you are having a boy or a girl, but only if the baby is in a position that allows a clear view. If you want to know, tell the sonographer at the start.

If you do not want to know the sex, let the sonographer know so they can avoid revealing it. Some hospitals have policies against telling you at the anomaly scan, while others are happy to do so.

Frequently Asked Questions

When is the anomaly scan done?

It is performed between 18 and 21 weeks, typically around 20 weeks.

Can it detect all problems?

No scan detects every condition, but it identifies many major structural abnormalities.

Can I find out the sex at the anomaly scan?

Often yes, if the baby is in a good position. Tell the sonographer if you want to know.

Summary

The 20-week anomaly scan is a detailed and important check on your baby development. Most scans are reassuringly normal, and your healthcare team supports you every step of the way.