Amniocentesis is an optional prenatal diagnostic test used to determine if a baby has any chromosomal abnormalities. A thin needle is used to remove fluid from around the baby. This fluid contains cells from the baby that are sent to a laboratory for genetic testing.
Who might consider an amniocentesis?
There are a variety of reasons why a pregnant woman might have an amniocentesis. Some reasons include:
Abnormal first trimester screen or quad screen
Family or personal history of chromosome abnormality or genetic conditions
Previous pregnancy/child with a genetic condition or birth defect
A woman over the age of 35
Any pregnant woman with a desire for a definite chromosomal assessment
When is an amniocentesis performed?
Amniocentesis is typically performed between the 16th and 24th week of pregnancy.
What are the benefits of amniocentesis?
It can detect nearly all chromosomal abnormalities, including Down syndrome, trisomy 13, trisomy 18 and sex chromosome abnormalities.
The test result provides a yes/no answer for the question: “Does my baby have a chromosome abnormality?”
If indicated, it can detect several hundred genetic disorders, such as Cystic Fibrosis, Sickle Cell disease, and Tay-Sachs disease.
Unlike Chorionic Villus Sampling, an amniocentesis can test for open neural tube defects, such as spina bifida.
The detection rate for chromosomal abnormalities is over 99% and 98-99% of open neural tube defects.
What happens during an amniocentesis?
The patient meets with a genetic counselor before the procedure to discuss the risks and benefits of an amniocentesis and to sign a consent form. Ultimately, the patient decides whether or not she would like to have the procedure.
To perform the procedure, the doctor uses ultrasound to determine the location of the placenta and the baby. A thin needle is then inserted in the patient's abdomen, through the uterus, and into the amniotic sac. About 1-2 tablespoons of the amniotic fluid that surrounds the baby is removed. The fluid is quickly replaced by the baby. The amniotic fluid contains skin cells that have naturally come off the baby during development. These cells have the same genetic makeup as the baby. The sample of cells from the amniotic fluid is tested for genetic disorders or chromosomal abnormalities. The appointment takes about 45-60 minutes, although the extraction itself will only last a few minutes.
What does amniocentesis feel like?
Overall, most women do not describe the procedure as being painful. Some women describe a sensation like a needle poke with discomfort in the abdominal area, similar to menstrual cramps. Some women may experience some mild cramping or light spotting for a few hours after the procedure.
How long do results take?
Final results are usually ready 7-10 days after the procedure. A genetic counselor calls the patient with results as soon as they are ready. A copy of the results is sent to the patient’s doctor or midwife.
Are there any special preparations for amniocentesis?
No. There are no dietary restrictions for amniocentesis. You do not need a full bladder. This test does not require an overnight stay in the hospital.
Patients should avoid heavy lifting (more than 20 lbs), strenuous activity and intercourse for 1-2 days after having the procedure.
After the procedure, the patient needs to call her doctor or midwife immediately if she experiences:
Loss of amniotic fluid vaginally
There is a very small risk of having a complication or miscarriage after the procedure.
Does insurance cover amniocentesis?
It is recommended that you check with your insurance company to verify coverage.
If you have additional questions, please feel free to contact The Center for Perinatal Care at 608-417-6667.