Amniocentesis & CVS


The amniocentesis is frequently done after week 15 of your pregnancy, or occasionally later if required. The procedure usually takes around ten to fifteen minutes to complete. During an ultrasound scan a needle is used to extract a small sample (between 10 and 20 ml) of the amniotic fluid, which surrounds the baby in the womb. This is done during a ultrasound scan so that the baby and the needle can be watched constantly. Because the fluid that is removed contains cells that have been shed by the developing fetus it means that these cells can be examined without any discomfort to the baby. You may feel some discomfort during the procedure and you may suffer with mild cramps afterwards. This test usually takes 10 days or more to get results and is the most accurate diagnostic test that is nearly 100% accurate.


Risks of the amniocentesis procedure

Like any procedure, amniocentesis is not risk-free. Because there is a slight risk of miscarriage you must discuss your concerns fully with your doctor beforehand as well as your partner. You have to make the very real decision of whether you want to know what conditions your baby may have developed against the risk of losing your pregnancy.


Chorionic villus sampling (CVS)

Chorionic villus sampling (CVS) is a test used to diagnose different genetic disorders including Trisomy 18. This test can be done when your baby has been diagnosed with T18, you have had a prior pregnancy with T18, or for women who are over the age of 35, who are at higher risk of their pregnancy having a chromosomal defect.

CVS is done by taking a biopsy of your placenta; a small sample of your placenta is tested. Chorionic villi are small finger shaped growths found in the placenta and the cells from the chorionic villi are the same as the fetus. This procedure is often done between the 10th and 12th week of pregnancy, but can be done as early as the 5th week.

This test can be done two different ways:

  • Inserting a thin catheter through the vagina and the cervix into the placenta is one way of collecting the sample. (transcervical).
  • Guiding a thin needle through the belly into the placenta is a second way that a sample can be collected. (transabdominal)

Ultrasound is used to guide the needle and/or catheter (tube) to make sure that needle is going into the correct location for sampling the placenta.


Risks of having this procedure done include:

  • Chance of miscarriage (0.5- 1%)
  • Infection
  • Amniotic fluid leakage (rupture of membranes)
  • Bleeding
  • Cramping

If you have any of these symptoms above you should contact your healthcare provider. Also contact your doctor if you have chills and/or fever.