What is an amniocentesis?  

An amniocentesis is a prenatal diagnostic procedure typically performed by a Maternal Fetal Medicine specialist that can be done during the second trimester of pregnancy (typically between 16 and 22 weeks) to test your baby for chromosome and genetic conditions.  

Amniocentesis involves using the ultrasound to guide a very thin needle through your abdomen and uterus (not belly button) to obtain fluid from around the pregnancy and send to the lab for testing.  With amniocentesis there is a risk for complications that can lead to a miscarriage.  This risk is significantly less than 1%.  

What does amniocentesis test for? 

There are many different types of testing that can be done on amniocentesis samples, including traditional chromosome analysis (karyotype), FISH, chromosomal microarray, and familial mutation testing.  All of this testing is considered to be diagnostic testing for chromosome and genetic conditions, meaning it can typically provide a ‘yes’ or ‘no’ answer, as opposed to screening tests which only tell you the chances or odds.  

Amniocentesis can test for many things, but cannot screen for all medical conditions or birth defects. Your physician or genetic counselor can help you understand the available testing options and interpret results.

Who can have an amniocentesis?

Amniocentesis is available to all women who are pregnant and desire to know more information about their baby’s chromosomes.  It is also available to women whose pregnancies are known to be at a higher risk for chromosome and genetic conditions based on screening and ultrasound results or family history.   It is important to know that prenatal diagnostic tests, like amniocentesis, are always optional. You never have to undergo any if you do not wish to. Anyone who is having prenatal testing should have access to all of the necessary information to make an informed decision about what is right for them and their family.