Why ultrasound baby scans are used during pregnancy, what to expect during an ultrasound scan plus checks on your foetus that can be made using ultrasound pictures.
Having an ultrasound scan in early pregnancy can be exciting; after all, you may be able to 'see' your baby for the first time.
Doctors and midwives use ultrasound scans to help assess the progress of the pregnancy and to identify whether there are any possible problems. It is important that you understand that if you have a scan and a potential problem is found you may have to make some difficult decisions.
It is up to you whether you have a scan. Most pregnant women are offered one but the research shows that your pregnancy will be just as safe if you do not have one.
Why are scans used?
There are four main reasons why scans are used in early pregnancy.
- To check when your baby is due.
- To see if there is anything wrong with the way your baby is developing.
- To check the position of the placenta (or afterbirth).
- To see if you are expecting twins, triplets or more.
Your baby's body is measured during a scan. This means that the person doing the scan can work out when the baby is likely to be born (the due date). This is considered to be more accurate than using a calendar and the date of your last period. One in five women have their due dates changed after their scans, in most cases the date is put later. This is useful, especially if you are unsure of your dates. It means blood tests can be interpreted more accurately. It could also help doctors know how many weeks old your baby is if you go into labour early. It can also mean that you are less likely to be offered an induction of labour because your pregnancy is thought to have gone past your due date.
Scans can often pick up early signs that a baby is not developing properly. If the signs suggest the possibility of a problem with the baby's chromosomes (like Down's syndrome), you will then usually be offered other tests before deciding whether to go on with the pregnancy or not. However scans are not perfect and may show a very minor problem or something which may get better on its own, so they can make you worry for nothing.
Scans do not pick up everything; some problems are missed. Only around half of major malformations are picked up on scans. For conditions like spina bifida (a problem with the baby's spine) detection rates are higher than this; for heart problems, detection rates are lower.
A scan can tell you the position of the placenta, particularly when it is lower than it should be in your womb. This information can be useful as a low placenta can cause problems towards the end of pregnancy. It could block the baby's passage out of the womb and more importantly cause serious bleeding. For the few women who, do have a placenta that remains too low, finding the problem early may be safer.
Having a scan means you will know sooner if you are expecting twins or triplets or even more! But even without a scan, most twins and triplets are detected before they are born.