

Chorionic villus sampling is usually done between weeks 10 and 12 of pregnancy — earlier than other prenatal diagnostic tests, such as amniocentesis.

You might consider chorionic villus sampling if:

  • You have a family history of a specific genetic condition, or you or your partner is a known carrier of a genetic condition. In addition to identifying Down syndrome, chorionic villus sampling can be used to diagnose many other genetic conditions — such as Tay-Sachs and cystic fibrosis.

Chorionic villus sampling can't detect neural tube defects, such as spina bifida. If neural tube defects are a concern, an ultrasound or genetic amniocentesis might be recommended instead.


  • Vaginal bleeding or spotting in the previous two weeks
  • A cervical infection
  • Cervical narrowing or blockage (cervical stenosis)
  • Involuntary spasms of the muscles of the vaginal wall (vaginismus)


  • Your uterus is severely titled backward and you have intestinal loops between your abdominal wall and uterus
  • Your placenta is located at the back of your uterus and your baby is blocking access to it


Your health care provider might caution against both types of chorionic villus sampling if you're Rh negative, your baby's father is Rh positive and you're sensitized — your body has already begun to produce antibodies after exposure to the baby's red blood cells at some point during pregnancy. If you're sensitized and have chorionic villus sampling, you're at increased risk of complications following chorionic villus sampling.

Oct. 10, 2012