Your baby's health and chorionic villus sampling

Every pregnant woman has concerns and questions about the health of her baby. Many factors play an important role in determining a baby's health. These factors include the age of the mother as well as genetic, medical and family histories.

Kapi'olani Medical Center for Women & Children offers prenatal diagnostic tests to help assess the health of a baby before it is born. Two common examples of prenatal diagnostic tests are chorionic villus sampling (CVS) and amniocentesis.

Below are answers to some of the most common questions about CVS. If you decide to have this test, your doctor or genetic counselor will answer any questions you may have.

What is chorionic villus sampling?

CVS is one method of prenatal diagnosis. It has been available to women for more than 10 years. The procedure is usually performed 10 1/2 to 13 1/2 weeks after your last menstrual period (when you are about three months pregnant). The advantage of CVS is that the health of the fetus can be assessed very early in pregnancy. Using ultrasound, the doctor will determine the position of the placenta. Then, depending upon its position, one of the two CVS techniques will be selected:

• TRANSCERVICAL CVS: using ultrasound guidance, a thin hollow tube is inserted through the vagina and cervix to the edge of the placenta and a sample of tissue is taken.
• TRANSABDOMINAL CVS: performed much like amniocentesis. Using ultrasound guidance, a thin needle is inserted through the abdomen to the placenta and a sample of tissue is taken.

Either technique takes just a few minutes.

The tissue removed is part of the finger-like projections of the developing placenta called villi. Cells from the villi tissue sample are allowed to grow in special lab conditions for several days and are then analyzed. Because the placenta and fetus develop from the same fertilized egg, the genetic material is usually the same. That's why CVS provides a good indication of the health of the fetus.

What problems can it detect?

• Careful study of the cells will identify chromosome problems, such as Down Syndrome.
• When a history of genetic disorder is known in a family, specific testing may be available through DNA or enzyme analysis. Ultrasound at the time of CVS cannot detect all major birth defects. A follow-up ultrasound examination at about 18 weeks of pregnancy is usually recommended.

It is important to note that Neural Tube Defects, such as spina bifida and anencephaly, cannot be detected by CVS. Therefore, women who choose CVS will also need a simple blood test (MSAFP) at 15-20 weeks of pregnancy. This will be arranged by your doctor.

No method of prenatal testing can guarantee that a baby will be born without birth defects, genetic disease or mental retardation.

Who should consider CVS?

Women should consider CVS if they:

• Are 35 years of age or older at delivery.
• Have a child or other relative with a chromosome abnormality, such as Down Syndrome
• Have a child or other relative with a detectable genetic disorder, such as Thalassemia or Muscular Dystrophy.

How accurate are the results?

Chromosome results and DNA studies are more than 98% accurate.

Occasionally, results need to be clarified through further testing.

How long do the test results take?

Results of CVS are usually available in two weeks. Special studies may take longer.

Is the procedure painful?

Either transcervical or transabdominal CVS may be uncomfortable. The transcervical method feels similar to having a pap smear. The transabdominal method is similar to having blood drawn where you feel a pinch and then some pressure. Some women experience no discomfort at all.

What should I expect after CVS?

Generally, women are able to return to their normal activities following CVS. Some women experience mild cramping and spotting after the test, but this usually resolves without further complication. If you elect to have CVS, you will receive more information on what to expect following the procedure.

Is there any risk with CVS?

Throughout pregnancy, there is always a natural risk of miscarriage. CVS increases the normal risk of miscarriage by approximately 1%. Your doctor or genetic counselor will discuss any other potential risks.

What special preparation is required?

You will need a full bladder. Drink at least two to four glasses of water before your appointment. You may also eat a light meal. Wear comfortable clothing. Please be prepared to discuss your family's health history.

Why choose Kapi'olani for prenatal testing?

The Fetal Diagnostic Center at Kapi'olani Medical Center for Women & Children is staffed by highly qualified, board-certified doctors and genetic counselors who specialize in prenatal diagnosis. Call the Fetal Diagnostic Center at 983-8559.

We hope this information has answered most of your questions about CVS. Your genetic counselor will explain this information in greater detail during your counseling session. To schedule an appointment, please call your physician. Meanwhile, take a few moments to write down any questions or concerns you have and bring them with you to your counseling session. We look forward to meeting with you.

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