OHSU

Prenatal Testing Options

The following medical tests are available during pregnancy to gather information about the health of your developing baby.

Screening Tests

Screening tests gather information about the possibility of a health problem in your developing baby during pregnancy. These problems may be due to a chromosome abnormality or birth defect.

Screening generally poses little or no risk to your pregnancy. Some examples include:

First trimester screening, such as the Sequential Screen

The test gathers information about the possibility that your  baby has Down syndrome, trisomy 18, or open spina bifida. The results are compared to a woman’s risk based on her background and age. If you are at an increased risk, you  may be offered further ultrasounds or diagnostic testing.

  • The detection rate for Down syndrome and trisomy 18, once the screening is complete, is 90 percent.
  • The detection rate for open spina bifida is 80 percent.

This screening test combines an ultrasound in the first trimester, plus blood work in the first and second trimesters of pregnancy. 

  • The ultrasound and first blood draw is performed between 11 weeks and the end of  your 13th week of pregnancy. 
  • The second blood test is typically done between weeks 15-21 of your pregnancy.

 

Second trimester maternal serum screening, such as the Quadruple or Penta Screen

The Quadruple marker screen (some laboratories now use the Penta Screen) measures chemicals in a woman’s blood that are produced during pregnancy. The levels of these chemicals give information about the possibility, or chance, that the baby has Down syndrome, trisomy 18, or open spina bifida. If you are at an increased risk, you may be offered further ultrasounds or diagnostic testing.

The detection rate for Down syndrome, trisomy 18, and open spina bifida is 80 percent.

Blood is typically drawn between weeks 15-21 weeks of your pregnancy.

 

Fetal DNA Testing

Fetal DNA can be tested using sample of the mother's blood. About Fetal DNA Testing

Diagnostic Tests

Diagnostic tests are able to tell accurately whether your developing baby has a chromosome abnormality or specific genetic disorder. There is a small risk to your pregnancy when these tests are performed. Diagnostic tests include.

Chorionic Villus Sampling (CVS)

This is a test typically performed between 11 weeks and the end of the 13th week  of your pregnancy. Our doctors use ultrasound guidance to obtain a small sample of the placenta from inside the uterus. There is no need to touch your developing baby or go into the amniotic sac with this test.

The sample of the placenta can be taken by inserting a small, flexible tube into the vagina and through the cervix.  Or a needle can be placed through the abdomen and into the uterus and placenta. The tissue from the placenta is then sent to the laboratory for chromosome analysis or genetic testing.

  • There is thought to be about a one  percent risk for complications related to the CVS procedure including bleeding, cramping, infection and miscarriage.
  • Results typically take between one to two  weeks and are 99.9 percent accurate.


More information on Chorionic Villus Sampling

 

Amniocentesis

This is a test typically performed between weeks 15-21 of your pregnancy. Our doctors use ultrasound guidance to insert a thin needle into the abdomen and uterus. This allows them to obtain about two to three tablespoons of the amniotic fluid that surrounds the developing baby.  There is no need to touch the developing baby with this test. The amniotic fluid is then sent to the laboratory for chromosome analysis or genetic testing.

  • There is thought to be less than a 0.5 percent risk for complications related to amniocentesis. These risks include  bleeding, cramping, infection and miscarriage.
  • Results typically take about two weeks and are 99.9% accurate. 


More information on Amniocentesis