What is an Ultrasound Scan?

An ultrasound scan is a procedure that uses high frequency sound waves that bounce off the baby in your womb and uses echoes to create an image of your baby.

When are scans done?  Many women have at least one scan in pregnancy but some women do not wish to have any scans.

Dating Scan 
Done in early pregnancy if the woman is unsure of her dates although a more accurate dating scan is ideally done between 10-13 weeks pregnant when a crown -rump length is measured.  Later dating scans will measure the baby's head circumference and the gestational age will be estimated.  This scan can also detect if you are expecting one baby, twins or more.  It is also done to identify the cause of any vaginal bleeding or pelvic pain and to see if your baby is developing in the womb and not in the Fallopian tube (ectopic pregnancy).

Nuchal Translucency Scan (NT)
Done between 11 weeks - 13 weeks and six days, this scan measures the fluid around the back of your baby's neck to assess your chances of having a baby with Downs Syndrome.  The nuchal translucency is usually done in combination with maternal serum screening (first trimester screening).

Anatomy Scan
This scan is performed between 18-20 weeks pregnant.  This scan will measure the baby's gestational age, size, weight of the baby and position of the baby.  The sonographer (person who  carries out the scan) will also check your baby's body to see if any problems.  Your placenta will be checked to see where it is situated in your womb and to check the fluid (liquor) volume that surrounds baby.  There are many abnormalities that cannot be detected in the womb.  If any concerns have been picked up by the scan, your midwife will refer you to the Consultant obstetrician.

Although you are excited to have a scan, it is not just to identify what sex your baby is but done to detect any problems your baby may have.  It also may not be possible to see if what sex your baby is because of his/her position in the womb.

Scans for other reasons
Amniocentesis or Chorionic villi sampling (CVS) to check the location of the placenta and the position of your baby.
Growth scans.  These are performed on a more frequent basis if there are concerns for the growth of your baby or you have had a previously small baby.
For diabetes, twins or any other medical conditions.

How is an ultrasound scan carried out?

The scan is done by a trained sonographer who has a postgraduate diploma or Masters degree in ultrasound scanning.  If you having a special procedure such as an amniocentesis or CVS, the scan will be performed by an Obstetric Consultant.

If you are having a dating scan or nuchal translucency, you will need to drink at least 3 glasses of water an hour before your appointment to esure you have a full bladder.  This helps to push your uterus out of your pelvis to give the sonographer a good view of your baby.  He/She will put some gel on your tummy and move a hand held device to get an image of your baby.

It is not always possible to get a clear image of your baby using abdominal ultrasound and sometimes the sonographer will carry out a vaginal scan.

An ultrasound scan does not hurt but if you have a full bladder there may be mild discomfort, if you are in pain, please let the sonographer know.

When your scan is completed the sonographer will give you an image of your baby to keep and may be in the form of a picture or DVD.

Are there any risks with an ultrasound scan?
Although to date, the results of follow-up studies on patients and children
who had been examined before birth have not demonstrated a causal link between adverse health effects and ultrasound exposure (Australasian Society for Ultrasound in medicine) it would be wise to limit the number of ultrasound scans performed in pregnancy.