Ultrasound is used during pregnancy to check the baby’s development and to help pick up any abnormalities such as Down syndrome. Since the procedure can’t produce high quality images, any suspected abnormalities need to be confirmed with other tests. The ultrasound scan isn’t 100 per cent accurate, but the advantages of the test are that it’s non-invasive, painless and safe for both mother and unborn baby.
First trimester - ultrasound performed within the first 3 months of pregnancy is used to check that the embryo is developing inside the womb (rather than inside a fallopian tube, for example), confirm the number of embryos, and calculate the gestational age and the baby’s due date. Second trimester - ultrasound performed between weeks 18 and 20 is used to check the development of fetal structures such as the spine, limbs, brain and internal organs. The size and location of the placenta is also checked. The baby’s sex can be established, if the parents wish to know. Third trimester - ultrasound performed after 30 weeks is used to check that the baby is continuing to grow at a normal rate. The location of the placenta is checked to make sure it isn’t blocking the cervix.
Ultrasound is a scan that uses high frequency sound waves to study internal body structures. The sound waves are emitted from a vibrating crystal in a handheld scanner. The reflected sound waves or ‘echoes’ are then translated into a grainy, two-dimensional (or sometimes three-dimensional) image on a monitor.
