Most hospitals will offer women at least two ultrasound scans during their pregnancy. The first is usually around eight to 14 weeks and is sometimes called the dating scan because it can help to determine when the baby is due. The second scan usually takes place between 18 and 20 weeks and is called the anomaly scan because it checks for structural abnormalities.
Ultrasound scans use sound waves to build up a picture of your baby in your uterus. They are completely painless, have no known serious side effects on mothers or their babies, and may be carried out for medical needs at any stage of pregnancy. If you have any concerns about having a scan, talk it over with your midwife, GP or obstetrician.
At the scan
You may be asked to drink a lot of fluid before you have the scan. A full bladder pushes your uterus up and this gives a better picture. You then lie on your back and some jelly is put on your abdomen. An instrument is passed backward and forwards over your skin and the high-frequency sound is beamed through your abdomen to the uterus and pelvis.
The sound is reflected back and creates a picture that is shown on a screen. It can be very exciting to see a picture of your own baby moving about inside you.
Ask for the picture to be explained to you if you cannot make it out. It should be possible for your partner to come with you and see the scan. Although scans are medical procedures, many couples feel that they help to make the baby real for them both. Ask if it’s possible to have a copy of the picture. There may be a small charge for this.
What do scans tell us?
• Check your baby’s measurements. This gives a better idea of when your baby was conceived and when it is likely to be born. This can be useful if you are unsure about the date of your last period or if your menstrual cycle is long, short or irregular. Your due date may be adjusted depending on the ultrasound measurements.
• Check whether you are carrying more than one baby.
• Detect some abnormalities, particularly in your baby’s head or spine.
• Show the position of your baby and your placenta. Sometimes a cesarean section is recommended - for example, if your placenta is low lying in late pregnancy.
• Check that your baby is growing and developing as expected (this is particularly important if you are carrying twins or more).
Fetal movement
You will usually start feeling some movements between 16 and 22 weeks. Later in pregnancy, your baby will develop its own pattern of movements - which you will soon get to know.
These movements will range from kicks and jerks to rolls and ripples and you should feel them every day. At each antenatal appointment, your midwife will talk to you about the pattern of movements. A change, especially a reduction in movements, may be a warning sign that your baby needs further tests. Try to become familiar with your baby’s typical daily pattern and contact your midwife or maternity unit immediately if you feel that the movements have changed.