Chorionic Villus Sampling

Chorionic Villus Sampling

What is chorionic villus sampling?

Chorionic villus sampling (CVS) is a prenatal test that diagnoses chromosomal abnormalities such as Down syndrome, as well as a host of other genetic disorders. The doctor takes cells from tiny fingerlike projections on your placenta called the chorionic villi and sends them to a lab for genetic analysis.

CVS and another test called amniocentesis produce a karyotype – a picture of your baby’s chromosomes – so that your caregiver can see for sure if there are any problems.

Women who choose to have CVS or amniocentesis are often those at increased risk for genetic and chromosomal problems, in part because these tests are invasive and carry a small risk of miscarriage.

The main advantage of CVS over amniocentesis is that you can have it done earlier — generally between 10 and 13 weeks of pregnancy. For an amnio, you’ll have to wait until you’re at least 16 weeks pregnant.

What kind of problems does CVS diagnose?

Like amniocentesis, CVS can identify:

  • Nearly all chromosomal abnormalities, including Down syndrome, trisomy 13, trisomy 18, and sex chromosome abnormalities (such as Turner syndrome). The test can diagnose these conditions, but it can’t measure their severity.
  • Several hundred genetic disorders, such as cystic fibrosis, sickle cell disease, and Tay-Sachs disease. The test is not used to look for all of them, but if your baby is at increased risk for one or more of these disorders, CVS can usually tell you whether he has the disease.

Chorionic Villus Sampling

Unlike amniocentesis, CVS cannot detect neural tube defects, such as spina bifida. If you opt for CVS, you’ll be offered a blood screening test in your second trimester to determine whether you’re at increased risk for neural tube defects. Most neural tube defects can be detected by a detailed second-trimester ultrasound done at a state-of-the-art academic center.

Be aware that if you have CVS, there’s a 1 to 2 percent chance of getting an unclear result. This is called a confined placental mosaicism, in which some of the cell lines cultured from the placenta contain abnormal chromosomes and some are normal. If your CVS detects a mosaicism, you’ll have to have amniocentesis and possibly other testing to determine whether your baby is affected.

Is there any way to reduce the risks of CVS?

Ask your practitioner or genetic counselor to refer you to an experienced doctor who does a lot of CVS procedures and who is expert at both the transabdominal and transcervical procedures, so your doctor can choose the procedure that’s safest for you. You may also want to ask about the estimated rate of procedure-related miscarriage for the doctor or the center where you’re considering having the procedure done.

You’ll also want to make sure that an experienced registered diagnostic medical sonographer provides continuous ultrasound guidance during the procedure. This greatly increases the chances that the doctor will be able to obtain enough tissue on the first try, so you won’t have to repeat the procedure.


Fetal Surgery

Fetal Surgery

Of the approximately 4 million babies born in the United States each year, about 120,000 (3 percent) have a complex birth defect. Maternal-fetal specialists have long known that some birth defects could be successfully treated after birth. But as technology, fetal imaging and prenatal testing have improved in the past few decades, so too has our knowledge of fetal development.

Expanded diagnostic tools have allowed us to identify more precisely when conditions worsen during fetal development. This knowledge has helped us develop new ways to help babies sooner while in utero. Today, fetal therapy is recognized as one of the most promising fields in pediatric medicine, and prenatal surgery is becoming an option for a growing number of babies with birth defects.

Fetal Surgery

Treating birth defects before birth

Fetal surgery allows us to intervene earlier. Using highly sophisticated surgical procedures, we are now able to treat certain disabling and life-threatening birth defects during fetal development instead of after birth, and to offer new hope to families.

Fetal surgery is a complex and challenging procedure, requiring the most expert, comprehensive care for both mother and unborn baby. Few medical teams have the skill and resources to perform such complex procedures, which can present significant risks for both mother and baby.

The Center for Fetal Diagnosis and Treatment at Children’s Hospital of Philadelphia has been providing this care to patients since 1995, experience that helps us to deliver the best outcomes while minimizing the risks to both you and your baby. Be sure to ask these questions before you allow a clinical program to perform fetal surgery.