The 20 week ultrasound

The 20 week ultrasound is probably the most important scan in pregnancy. All pregnant women need to have this scan. It looks for abnormalities in your baby’s anatomy, so it’s also called the fetal anatomy or morphology scan. An estimated 2-3% of women will have a problem identified.

During the 20 week ultrasound we perform a detailed head-to-toe examination of the baby, aiming to:

  • Identify structural fetal abnormalities
  • Check the location of the placenta and the amount of fluid
  • Measure cervical length to identify women at high risk of premature birth
  • Check fetal size and perform uterine artery Dopplers in women at high risk of fetal growth restriction
  • Check the fetal gender (if the parents wish and the baby co-operates!)

However, not all congenital problems can be detected on ultrasound:

  • The 20 week ultrasound only provides information on fetal anatomy, not childhood development. It does not tell us anything about behaviour, intelligence or personality
  • Some fetal structural or genetic problems are very subtle and may not be visible on ultrasound scan at any stage of pregnancy
  • The ability to detect fetal problems depends on the image quality. Sometimes babies lie in the wrong position and it’s not possible to see all the anatomy. Image quality may also be reduced in larger women. You may need a follow-up scan in these circumstances.

Dr Walsh is a recognized expert in fetal anatomy ultrasound. He scans both low-risk and high-risk patients. You are also welcome to see him for 2nd and 3rd opinion scans (where a problem is suspected and needs further confirmation and advice). As a Maternal-Fetal Medicine Obstetrician he specializes in the diagnosis and management of fetal abnormalities.

We offer the full range of specialist obstetric ultrasound scans. Please click on the links below for more information :

Fetal Anatomy