Ultrasound Scans

Ultrasound scans

During an ultrasound scan high frequency sound waves are transmitted through the uterus.  The sound waves bounce off the baby and the returning echoes are translated by a computer into an image on a screen that reveals the baby’s position and movements.  Soft tissues appear grey, while hard tissues such as bone reflect the biggest echoes and appear white.  Fluids, such as the amniotic fluid, are unable to reflect any echoes and appear black.  It is the contrast between these different shades of white, grey and black that allows your sonographer to interpret the image.  The main purpose of the ultrasound scan is to check that your baby is growing and developing normally.

Did you know?

Scans are usually performed by radiographers or gynecologists who are specially trained in ultrasound, and are known as sonographers. 

What is an ultrasound scan used for?

Depending on which stage of pregnancy they are done at, ultrasound scans can:

• Check that your baby has a heart beat;
• Determine whether you are pregnant with one baby or more;
• Detect an ectopic pregnancy;
• Determine the cause of any bleeding you might be having;
• Accurately determine your due date by measuring your baby;
• Conducting a Nuchal Translucency Scan whereby the fluid at the back of your baby’s neck is measured to assess the risk of Down’s syndrome and other abnormalities;
• Find out why a blood screening test was abnormal;
• Assist in performing diagnostic tests, such as CVS or amniocentesis safely by showing the position of the baby and placenta;
• To examine your baby to see whether all the organs have developed normally;
• To diagnose certain abnormalities such as spina bifida;
• To measure the baby’s growth rate over several scans during your pregnancy;
• To reveal the sex of the baby from about 18 weeks, provided that the baby is laying correctly.  It must be noted that it is not usually possible to be 100 percent certain of the sex of your baby.

How is the scan done?

The sonographer will put some cold gel on your tummy and will move a small hand-held transducer over your skin to get views of the baby.  The scan is painless except for the discomfort of the transducer pressing on your tummy if you have a full bladder.

If your baby is still too deep in your pelvis, the images will not be very clear, so a vaginal scan may be necessary.  The vaginal transducer is long and narrow to fit comfortably inside your vagina.  The sonographer will use a cover similar to a condom and will lubricate this with plenty of gel so that it would slide in easily.  A vaginal scan is best done with an empty bladder, and if you relax your muscles so that the transducer can slide in easily, it should not be the least bit uncomfortable, although you may feel a bit embarrassed.  It is not necessary to push the vaginal transducer in very deep, and it won’t harm you or your baby in any way.  Vaginal scans give a much clearer picture of your baby, especially at the very early stage of pregnancy.

Is ultrasound safe for your baby?

Medical research has found no association between ultrasound exposure and the baby’s birth weight, childhood leukemia or other cancers, eyesight and hearing problems or dyslexia.  However, experts agree that ultrasound exposure should be justified and limited to the minimum needed to make a diagnosis.

What if the scan shows a problem?

You will naturally be very worried if your scan suggests that there might be a problem with your baby.  Sometimes a definite diagnosis can be made from the scan, such as spina bifida.  In other cases the scan may show minor changes which may be a sing of a more serious problem, such as Down’s syndrome or might even turn out to be just a variation of normal.  If the sonographer finds anything unusual when doing the scan, you would immediately be referred back to your gynecologist (if it is different people) and further tests such as CVS or amniocentesis needs to be done to see if the baby’s chromosomes are normal.

In the unlikely event that your baby does have a serious problem, you will need time and support to think through your choices.  These may include ending the pregnancy or preparing for the birth of a baby who will need special care.