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Patient Information: Amniocentesis

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What is amniocentesis? 

Amniocentesis is a prenatal diagnostic test used to determine if a baby has any chromosomal abnormalities.

When is an amniocentesis preformed?

Amniocentesis is typically preformed between the 16th and 24th week of pregnancy.

How is the amniocentesis procedure done?

Amniocentesis is always done through the abdomen. First, an ultrasound is preformed to determine the location of the placenta and the baby. Next, a woman’s abdomen is wiped down with a sterilizing solution. Using ultrasound guidance, a thin needle is inserted though the abdomen and into the amniotic sac. A small amount of amniotic fluid (approximately 1-2 tablespoons) is removed. This fluid is easily replaced by the baby in the next few hours. The amniotic fluid contains skin cells that have naturally come off your baby during development. These skin cells are sent to a laboratory for analysis. The total procedure may take anywhere from 30-45 minutes, although the extraction itself only last a few minutes. 

What does amniocentesis feel like? 

Overall, most women do not describe the procedure as being painful. Some women describe discomfort in the abdominal area, similar to menstrual cramps. Some women may experience some mild cramping for a few hours after the procedure.

What kinds of disorders can amniocentesis detect?

Amniocentesis detects chromosomal disorders such as Down syndrome, trisomy 18, trisomy 13, and sex chromosome abnormalites. Amniocentesis does not diagnose all genetic conditions. However, if there is a known family history of a genetic condition, often genetic testing for that condition can be performed on the amniocentesis sample. Amniocentesis can also diagnose open neural tube defects (i.e. spina bifida or openings along the spinal column) by evaluating a protein (alpha-fetoprotein or AFP) found in the amniotic fluid. The detection rate for chromosomal abnormalities is over 99% and it can rule out between 98-99% of open neural tube defects.


Final results are typically available 7-10 days after the procedure. A genetic counselor will call you with the results as soon as they become available. A copy of the results will be sent to your primary care provider’s office.


The risk of complication due to amniocentesis may be as high as 1/300 (0.3%) although some resources report that it may be lower. This is in addition to the natural background miscarriage risk of 2-5%. Complications may include bleeding, cramping, loss of amniotic fluid vaginally, maternal infection or miscarriage.

How should I prepare for the amniocentesis?

There are no dietary restrictions. This test does not require an overnight stay in the hospital.

Do I have to have an amniocentesis?

No. Amniocentesis is completely voluntary. You will meet with a genetic counselor prior to the procedure to discuss the risks and benefits of amniocentesis. Ultimately you decide whether or not you would like to have this procedure.


Please feel free to contact us if you have any questions or concerns (608) 417-6667. Also, visit our website (unitypoint.org) for more information about other services provided at Meriter’s Center for Perinatal Care Clinic.