Chorionic villus sampling involves removing a small piece of the placenta to be examined in the laboratory. Placental and fetal cells are identical as both are created from the fertilization of an egg by sperm so examining the placenta is just like examining the fetus’s genetic makeup itself. There are two techniques used for chorionic villus sampling:

1. Transcervical chorionic villus sampling is done through the vagina. You will like on your back on the examination table with your knees bent and your vulva exposed to the doctor. The doctor will insert a tool into the vagina to visualize your cervix. The cervix will be disinfected. Ultrasound will be used to locate the placenta and the safest site from which to remove a small sample. A chorionic villus sampling catheter, which is a very small and thin tube, or forceps, will be used to remove the sample for examination.
2. Transabdominal chorionic villus sampling involves the use of a needle that is inserted through the abdomen to remove the sample. You will lie on your back on the examination table with your abdomen bare. (Please wear comfortable loose-fitting clothing.) The doctor will apply a cool gel to your stomach and use ultrasound to locate the safest site to introduce the needle into the placenta. The site will then be disinfected and a local anesthetic will be administered. The needle is then pushed through the abdomen and into the uterus to remove a piece of the placenta. This procedure is similar to an amniocentesis.

An amniocentesis carried out at 16 to 20 weeks of gestation.
 
It is recommended that all women at risk of birthing a child with health issues speak to their doctors about further testing, but ultimately all prenatal testing is the decision of the patient. Please carefully consider the risks of chorionic villus sampling and other procedures as well as their benefits to you and your child.