Ultrasound scans or sonograms

Ultrasound scans are also called sonograms or "scans".  In this test, sound waves are bounced off the baby's bones and tissues to construct an image showing the baby's shape, size and position in the uterus.  Earlier, ultrasounds were used only in high-risk pregnancies but have now become very common and are part of routine prenatal care.

Why are ultrasound scans used?

• To verify the due date
• To determine if the baby is growing at a normal rate
• To detect structural defects such as spina bifida, heart defects, cleft lip etc.
• To determine if there are multiples foetuses (for example twins)
• To ensure that there is enough amniotic fluid
• To indicate the position of the placenta (Later in the pregnancy it might block baby's way out of the uterus)
• As a guide during other tests like amniocentesis

When?

• Ultrasound scans are totally safe. These days, typically, the scans are performed two times during a pregnancy.
• The first scan is during the doctor’s appointment (late in the first trimester) to confirm the due date and to check for twins and the position of the baby in the uterus. This is also called the "dating scan".
• The second scan is at 18-20 weeks to check for structural defects (spina bifida, heart defects, congenital heart defects, cleft lip etc.) and baby’s growth. It is also called the “anomaly scan”.

Make a special note

• Women who have high-risk pregnancies (older than 35, carrying twins, other problems) might need many more ultrasounds.
• Also in the last trimester, if the doctor suspects that the baby is not growing as much, the doctor may advise additional scans to check baby’s growth - "growth scans".
• In India it is illegal to determine the gender of the baby because of the high rates of female foeticide.  Doctors and technicians do not disclose the gender of the baby even though they can. Before you go for the scan, you will be asked to sign a document which states that you will not ask the sonographer or the technician about your baby's gender.
• Technicians can tell the results instantaneously, but a full evaluation by your doctor might take about one week.

How?

• If you are having a scan in early pregnancy, your uterus is deep in your pelvis and it is difficult for the sonographer to get a good picture of your baby.  In this case, the sonographer might use a vaginal scan or an abdomen scan with a full bladder.
• In the vaginal scan, the transducer (the device that transmits the sound waves) is carefully inserted into your vagina.  It will be uncomfortable but will not necessarily hurt. The technician will lubricate your vagina with gel so that the transducer can be easily inserted.  Do not feel embarrassed because the technician does this routinely to many women many times a day. Many doctors use vaginal scans only in the very early appointment to date the pregnancy.
• Also, in the early pregnancy, abdominal scans with a full bladder are conducted.  The full bladder pushes the uterus out for a clear picture of the baby.
• In later parts of pregnancy, you can relax.  It is not necessary to do the cumbersome abdomen scan with a full bladder, because the uterus will be very prominent and poised for a clear picture—thanks to the growing baby.

Last updated: Oct 27, 2008