What Happens at an Ultrasound Scan?
An ultrasound scan is routinely offered to pregnant women at around 12-14 weeks (sometimes referred to as your early ‘dating’ or ‘booking’ scan).
In certain circumstances, for example, if there are any particular risks or problems, you may be able to have earlier or later scans if necessary.
How they work
An ultrasound scan transmits silent sound waves through your body tissues to create an image of your baby in your womb, which you and your partner will be able to see on a TV/computer screen.
Before having your abdominal scan, you’ll be asked to drink plenty of fluid and not to empty your bladder: if your bladder is full, it then pushes up against your womb to give a better view of your baby. This is really important in the first half of your pregnancy trimesters.
When you are lying down, a gel will be placed onto your stomach and a handheld probe/scanner/transducer will be moved in various directions over your skin to allow you to see your baby inside your womb.
Ultrasound scans can also be carried out using a vaginal probe. If this is the case, you will not normally need to have a full bladder as these types of ultrasound scans give a clearer picture, especially in early pregnancy.
While the scan is being carried out, the operator will usually explain what she/he is looking at, and you may be given a black-and-white printout of the picture to take home with you, as well as information and charts of various measurements. Some units also offer you the option to have your scan recorded on a video tape, which you can purchase.
Do ultrasound scans hurt?
Ultrasound scans are completely painless, and to date there’s no medical evidence to suggest that they can harm either the pregnant woman or her baby. In fact, seeing your baby moving around during the scan can be highly enjoyable and reassuring.
What they do
Ultrasound scans don’t take long to complete and are used for various reasons, although their main purpose is to check:
- whether you’re carrying more than one baby
- how far advanced in pregnancy you are : for example during the first trimester screening
- if your baby is developing normally and to monitor its growth and well-being.
Not only can ultrasound scans measure your baby’s size and shape, to give a better idea of age and date of delivery but they can also:
- show the exact position of your baby and the placenta (if your placenta is low, this may be an indication of placenta, which may affect delivery)
- assess bleeding in early pregnancy, and exclude an ectopic pregnancy
- identify fetal abnormalities, especially of the head or spine, such as the structural/developmental defects spina bifida and hydrocephalus, or for specifying the risk of the chromosomal disorder Down’s syndrome.
- show your baby moving and allow you to hear his/her heartbeat and see fetal movements, amniotic fluid volume and blood flow to the womb along the umbilical cord (also seen on a later scan)
- where possible allow you to find out the sex of your baby at the 20-week scan, but if you want to know you will probably have to ask. Some units, however, prefer not to tell you
- be used to guide certain pregnancy diagnostic tests or operations that may have to be undertaken on your baby in the womb.
Furthermore, some units now offer Doppler ultrasound scans as part of your regular scan to measure the blood flow to your womb. This may help to identify potential problems such as pre-eclampsia or a very small baby.