Amniocentesis

Amniocentesis is a prenatal diagnostic test performed between the 15th and 20th week of pregnancy.  This test is done to detect chromosomal abnormalities (such as Down syndrome) and neural tube defects in an unborn child.  In amniocentesis, a few tablespoons of amniotic fluid are withdrawn.  Amniotic fluid surrounds the baby and contains cells that come from the baby during the pregnancy.  These cells are cultured for about 10 days and a chromosome analysis is performed.  If a family is known to be at risk, other specialized tests may be performed. Genetic counseling is provided before each amniocentesis procedure.

Amniocentesis is also used to detect neural tube (brain and spinal cord) defects including spina bifida and anencephaly in the fetus.  Alpha-fetoprotein (AFP) is produced only by the fetus and is present in the fetal spinal cord.  The amount of AFP can be measured in amniotic fluid.  If there is more than the usual amount of AFP, an opening in the spinal column (neural tube defect) or other birth defect may be present.  Further testing is indicated to determine the nature of the possible birth defect in the fetus. 

The most common reasons couples consider undergoing amniocentesis are:

<!--[if !supportLists]-->·      <!--[endif]-->Women who will be 35 years or older at the time of delivery

<!--[if !supportLists]-->·      <!--[endif]-->Couples who have had a previous child with a chromosomal abnormality or metabolic disorder

<!--[if !supportLists]-->·      <!--[endif]-->Couples who have had a previous child with a neural tube defect

<!--[if !supportLists]-->·      <!--[endif]-->A parent who is a carrier for a chromosome rearrangement (translocation)

<!--[if !supportLists]-->·      <!--[endif]-->Parents who are both carriers of a recessive gene (Tay Sachs disease, sickle cell anemia, cystic fibrosis)

<!--[if !supportLists]-->·      <!--[endif]-->Women who are carriers for an X-linked disorder (fragile X syndrome, hemophilia)

<!--[if !supportLists]-->·      <!--[endif]-->Women who have had an abnormal AFP or quad screen result

Amniocentesis is an outpatient procedure. An ultrasound is performed prior to the procedure to determine the gestational age of the fetus, number of fetuses present, placental location and the site for needle insertion.  After sterile cleansing, a thin needle is inserted (generally below the navel) and approximately 2 tablespoons of amniotic fluid are removed.  During the procedure, women may feel slight cramping as the needle is inserted and some pressure as the fluid is withdrawn, but generally the procedure is not painful.

Heavy lifting and excessive physical activity are discouraged for 48 hours following the procedure, but no other special limitations are made on a patient's activity.  However, women should watch for signs of excessive bleeding, cramping, fever or leakage of fluid. 

Amniocentesis has been performed in the United States for more than 25 years. All of our physicians perform amniocentesis in all three locations.  The risk of minor complications including slight cramping, bleeding or leakage of amniotic fluid is approximately 2-3%.  The risk for miscarriage following the procedure is approximately 1/500. 

If you would like further information or to schedule an appointment, please call Maryland Perinatal Associates, PC at 301-251-8611.  Our genetic counselor is also available to answer any further questions about amniocentesis.