Reasons for testing
Understanding your testing options helps you prepare for the future.
Your reasons for testing may include:
- confirming your pregnancy and estimating your due date
- determining the presence of more than one fetus (twins)
- confirming placental position
- evaluating risk of Down syndrome early in pregnancy (nuchal translucency ultrasound between 10 and 13 weeks)
- often identifying your baby’s gender at 16 weeks
- evaluating risk for major physical birth defects. (This type of ultrasound is called a “comprehensive” ultrasound and is typically performed between 18 and 22 weeks at a highly specialized center.)
If you are not sure whether you should have ultrasound, please talk with your doctor. See “Questions to Ask Your Doctor”.
Testing for...
The ultrasound can be used during pregnancy to show images of your baby, amniotic sac, and placenta. Some major birth defects can be seen with an ultrasound.
How the test works
A prenatal ultrasound test uses high-frequency sound waves transmitted through your abdomen via a device called a transducer to view the inside of your abdomen.
With prenatal ultrasound, the soundwaves are recorded and transformed into video or photographic images of your baby. Your baby's heartbeat and movement of its body, arms and legs can be viewed on the ultrasound.
Most prenatal ultrasound procedures are conducted on your skin, using a gel as a conductive medium to improve the image’s quality.
A transvaginal ultrasound is an alternative procedure performed using a tubular probe inserted into your vaginal canal.
The transvaginal method produces a greatly enhanced image, but it is not a common prenatal procedure. It may be used early in pregnancy to get a clearer view of your uterus or ovaries and to determine how far along you are in your pregnancy (gestational age).
Ultrasound is performed by a doctor or sonographer. (Genzyme does not perform ultrasound.)
What's not detected
Every pregnancy has some risk (3-5%) for the kinds of birth defects that cannot be diagnosed during pregnancy, such as autism, non-specific mental retardation, some genetic diseases and many types of physical birth defects.
Understanding results
If an abnormality is identified, a follow-up with a perinatologist and/or genetic counselor may be recommended.
