Antenatal Scans

You’ll likely be offered an ultrasound scan to check that your baby is developing normally. Most parents relish the opportunity to see their baby on the screen in front of them, and fathers especially find it makes their baby more real for them.

Some parents worry about the long-term effects of ultrasound scans but numerous studies haven’t indicated any harmful effects. As a precaution, the American College of Obstetricians and Gynecologists recommends scans be given only when medically necessary. Don’t expect all the answers from your scan though: if your baby isn’t in a good position it may be difficult for the sonographer to see him properly. And they definitely aren’t infallible when it comes to revealing whether your baby is a boy or a girl!

What happens at an ultrasound scan?

Ultrasound scans work by bouncing sound waves off your baby to create an image on the screen. During the scan, the sonographer applies lubricating gel to your bump to help the sound waves conduct better, and then glides a handheld instrument called a transducer over your skin. Alternately, a vaginal transducer may be used, although this tends to work better for scans in early pregnancy. The sonographer will keep you informed as to what she’s looking at and you can ask questions about what you can see on the screen.

When will I have one?

Occasionally you may be offered a dating scan in your first trimester (weeks 0-12) if you’re unsure of your dates and are at risk of having a baby with an abnormality, since the accuracy of screening and diagnostic tests depends on when they’re performed. You may also have an early scan if there are any concerns about your pregnancy (for example, if you’ve experienced any bleeding or you conceived via IVF). 

Most women have what’s called the nuchal translucency scan as part of their first trimester screen between weeks 11 and 13. It screens your baby for signs of chromosomal disorders such as Down syndrome but doesn’t check for signs of neural tube defects such as spina bifida.

You’ll have a second ultrasound scan between 16 and 20 weeks. The sonographer will check that your baby is developing normally, particularly if you had a positive result on any of your screening tests. This scan is highly effective at picking up problems – neural tube defects such as spina bifida, kidney problems, limb abnormalities and defects of the abdominal wall are all likely to be seen if they exist. Other conditions, such as congenital heart problems and hydrocephalus (excess fluid on the brain) may also be diagnosed at this stage. Keep in mind though that this is still essentially a screening test and you would need to have an amniocentisis for a definite diagnosis.

It’s also at this scan that you may be told what sex your baby is going to be if you’d like to know – if you don’t want to, remember to warn the sonographer and avert your eyes when she starts moving south!

The information in this feature is intended for educational purposes only. If you have any concerns about your health, the health of your child or the health of someone you know, please consult with a doctor or other healthcare professional.

Related Articles

• Early Pregnancy: Ultrasound scans
• Guide To : Pregnancy: Antenatal care and Ultrasound scans
• Guide To : Pregnancy: When can the ultrasound detect twins?
• Guide To : Pregnancy: Which scans or tests show up any abnormalities?
• Tests & Checks: Dating Scan