Invasive Prenatal Testing Options

During your pregnancy, it is important for you to remember that:

• Most babies are born healthy

• Every pregnancy has a 2–3 percent chance of having a baby with some type of birth defect (such as a heart defect, cleft palate

• Not all birth defects can be detected during an ultrasound

Having prenatal testing in your pregnancy is your choice. There are several resources available to you to help you make a decision about invasive testing.

What is amniocentesis?

Amniocentesis is a medical procedure performed by a Maternal Fetal Medicine doctor trained to do procedures under ultrasound guidance. It is usually done between 15-18 weeks gestation. This test will give a diagnosis of specific chromosomal conditions if they are present. Most women do not have complications after their amniocentesis. Very rare complications, such as miscarriage or infection, may occur.

Who can have amniocentesis?

A woman may be offered amniocentesis when:

• she has a positive first trimester screen (FTS) greater than 1/300 or a high risk non-invasive prenatal screen (NIPS)

• fetal developmental differences have been seen on ultrasound that may be linked to a chromosomal condition

• she has a personal or family history of a genetic condition that the baby may also have

How is amniocentesis done?

An ultrasound is used to locate your baby’s position. A fine needle is carefully inserted into the uterus and one to two tablespoons (15–30 mL) of fluid is removed for testing. The ultrasound is continued throughout the test to monitor the baby’s heartbeat. The actual test usually takes only a few minutes. Once it is done you should rest for the rest of the day.

Problems, though uncommon, may come up during the procedure or in the laboratory:

• a technical difficulty getting an amniotic fluid sample based on the woman’s anatomy, the baby’s position or if the amniotic fluid is really low

• the cells do not grow, so no result is possible

• trouble interpreting the test results (you and your partner may be asked to give a blood sample to help interpret your baby’s chromosome result)

If there are any issues with your test, the Maternal Fetal Medicine doctor will talk to you about next steps.

What happens after the amniocentesis?

Avoid strenuous activity for a day after the procedure. You may have a small amount of bloody spotting for up to a week. The initial genetic test results are usually back in 3-5 business days but may take longer depending on the type of testing required. A nurse or Maternal Fetal Medicine doctor will call you directly with the results and discuss them with you.

What is chorionic villous sampling (CVS)?

Chorionic Villus Sampling (CVS) is another prenatal diagnostic test, done by a Maternal Fetal Medicine doctor, available to some women between 11+0 and 13+6 weeks of pregnancy. This procedure obtains a small sample of the developing placenta. The cells in the placenta are usually the same genetic make-up as the developing baby. This test will give a diagnosis of specific chromosomal conditions if they are present. Very rare complications, such as miscarriage or infection, may occur.

Who can have a CVS?

A woman may be offered a CVS when:

• she is between 11+0 and 13+6 weeks pregnant

• she has a positive first trimester screen (FTS) with a positive result greater than 1/100 or a high risk non-invasive prenatal screen (NIPS)

• fetal developmental differences have been seen on ultrasound that may be linked to a chromosomal condition

• she has a personal or family history of a genetic condition that the baby may also have

How is CVS done?

Using ultrasound guidance, CVS may either be done through the cervix (trans-cervical) or through the mother’s belly (trans-abdominal) to obtain a small sample of the developing placenta. The ultrasound is continued throughout the test to monitor the baby’s heartbeat. The actual test usually takes only a few minutes. Once it is done you should rest for the rest of the day.

Problems, though uncommon, may come up during the procedure or in the laboratory:

• a technical difficulty getting a placental sample based on the woman’s anatomy, the baby’s position or the placenta’s position

• the cells do not grow, so no result is possible

• trouble interpreting the test results (you and your partner may be asked to give a blood sample to help interpret your baby’s chromosome result)

If there are any issues with your test, the Maternal Fetal Medicine doctor will talk to you about next steps.

What happens after the CVS?

Avoid strenuous activity for a day after the procedure. You may have a small amount of bloody spotting for up to a week. The initial genetic test results are usually back in 3-5 business days but may take longer depending on the type of testing required. A nurse or Maternal Fetal Medicine doctor will call you directly with the results and discuss them with you.

Getting your results

If a chromosome condition is found in the baby’s cells, you may be referred to Medical Genetics. You will receive counselling to review your results, receive information about the condition that has been identified, and to review your options for pregnancy management.

If your baby’s result is normal, ongoing care will be planned by your prenatal care provider.

It is important to call your healthcare provider if you have any of the following after an amniocentesis or CVS:

• a fever

• painful contractions or worsening abdominal pain

• unusual or bloody drainage from the vagina

If you would like more information on invasive testing, you can talk to your health care provider or ask if you can be referred to Medical Genetics.