Glossary | Amniocentesis

Amniocentesis

An amniocentesis is a test done between 15 to 20 weeks gestation where a doctor, using a thin needle, will obtain a sample of amniotic fluid from your womb. The amniotic fluid contains cells from your baby that can be examined and the genetic makeup determined. This test is often done in order to determine if your baby carries a genetic condition such as Down syndrome. The results usually takes about 10 to 12 days to come back and is over 99% accurate . It can also be used to determine if your baby has a defect in its neural tube (the part of the body that will make up the spinal cord and the brain). Unfortunately, an amniocentesis can cause a miscarriage. The rate of having a miscarriage with an amniocentesis will vary but is usually quoted as being between 1 in 300 to 1 in 500. Do note that in about 1% of cases, will you experience some vaginal leakage or spotting after the procedure. In over 90% of cases, it will resolve on its own. Do talk to your doctor who will be performing it in order to learn what their miscarriage rate is. Due to the risk of a miscarriage it is important to take it easy for several days after the amniocentesis. There is no research showing exactly how long one should rest after an amniocentesis. However, several large medical centers recommend bed rest for 1 day, no lifting over 15 pounds (7kg) for 48 hrs, no strenuous exercise for 72 hours, no air travel for 72 hours and no intercourse for 7 days. A Chorionic Villus Sampling (CVS) is a method to obtain genetic information on your baby about a month prior to the amniocentesis. The miscarriage rate is felt to be a little higher with the CVS compared to the amniocentesis. Currently, many women choose to use a non-invasive method to determine if their baby has a genetic condition and only go on with an amniocentesis or CVS if this preliminary testing is not reassuring. The non-invasive testing involves a combination of an ultrasound, called nuchal translucency (NT) and blood tests done in the 1st and 2nd trimesters.