Article: Tina Otte from Your Pregnancy magazine
Image: preview

What a scan can tell you
Two dimensional ultra sound scans use high frequency sound waves which are transmitted through your abdomen using a piece of equipment called a transducer, then bounced off tissue and reflected back to a computer to be translated into a picture. Scans are useful for estimating the age of the baby and assessing his well being at any time during pregnancy. Scans show the growth of the foetus and are used for detecting birth defects.

Early scan
At five weeks the pregnancy sac is visible and between 6 and 7 weeks the embryo and heart movement can be seen, At eight weeks you'll start to see foetal movements and at this stage, twins can be confirmed. Between weeks 8 and 10 the outline of the placenta becomes visible and the first measurements can be made on the foetus to establish and confirm a due date.

12- 18 week scan
In this 12 week scan the organs become visible. The baby's head is measured to accurately date the pregnancy. The femur length is another important landmark for working out the age of the baby. Other important structures looked for in a routine scan include the stomach, the bladder, the spine and the external genitalia. The placenta is easily recognised from the rest of the uterus. The amount of amniotic fluid can be assessed at this time as well.

18 - 26 week scan
This is the most important routine scan because it gives an accurate assessment of the gestational age and most major abnormalities can be detected. This scan, at 24 weeks, is much more detailed than early scans because your baby's anatomy is fully formed. Conditions such as a low -lying placenta can be picked up or any abnormal characteristics of the uterus might make delivery more complicated.

Now in 3D
You can also see your baby in 3-Dimensional ultrasound. Several cross-sections of the baby are acquired and the individual sections are combined. When the image is complete, it can be viewed on the screen, rotated and tilted at any angle so that cheeks, nose, lips, and eyes can all be seen. This can only be done between 28 and 32 weeks but it does not give more information than 2D.