An ultrasound scan is done with the help of a sonar device that reveals objects in fluid (amniotic fluid in pregnancy) by using high frequency sound waves, inaudible to the human ear. An ultrasound scan is a non-invasive, painless procedure and usually lasts for about 15 minutes. You will probably be asked to drink few glasses of water and not urinate before arriving at the clinic.
Though a full bladder may be uncomfortable for you, it will help to get a clearer picture of the foetus on the screen. A jelly, which acts as a conductor of sound waves, is rubbed on your abdomen and the transducer is passed over this area in different directions to reflect your baby’s picture on the screen. Now, you can relax and enjoy the first view of your baby.
When can you have your first scan?
Your first ultrasound scan will be done as early as the sixth to the seventh week of pregnancy. This is to confirm intra uterine pregnancy and foetal well being including foetal cardiac activity. Your first scan will also help diagnose ectopic pregnancy and to assess threatened abortion.
Is an ultrasound safe during pregnancy?
Unlike an x-ray, ultrasound scanning poses no known risk to the foetus.
How many ultrasounds are done during pregnancy?
If your pregnancy is normal, you will have to go through three ultrasounds. Your second ultrasound will be done between 18 to 20 weeks to rule out any congenital anomalies of the foetus.
And the third ultrasound at around 37 to 38 weeks for the following reasons:
To check the baby’s growth and make a rough estimation of baby’s weight. This is particularly helpful if the last menstrual period date is doubtful.
To confirm the baby’s position (normally the baby should be in a head down position) as this will determine the mode of delivery.
To check the position of the placenta and its maturity. Normally, the placenta should be in the upper segment of the uterus. If the placenta is low lying and covering the mouth of the uterus, you have to be careful about vaginal bleeding and if the baby has to be delivered by caesarean section.
To confirm multiple pregnancy.
Special cases of ultrasound in pregnancy are done
To monitor the baby with special tests such as amniocentesis (little amount of fluid is taken out from the amniotic sac by inserting a needle under the guidance of an ultrasound machine to assess chromosomal abnormalities.)
To assist in the operations performed on the baby in the uterus.