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Amniocentesis

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Amniocentesis is a common prenatal test in which a small sample of the amniotic fluid surrounding the fetus is removed and examined. Amniocentesis prenatal test is used to diagnose chromosomal and genetic birth defects. Nearly 99% of all chromosomal abnormalities can be detected with an amniocentesis test. Are there any risks associated with amniocentesis ?


Amniocentesis Test

Amniocentesis test is carried out on a pregnant woman to collect information about the fetus from a sample of the amniotic fluid. The fetus is surrounded by the amniotic fluid inside the uterus. Amniocentesis is not advised to all pregnant women because it carries a small risk of miscarriage. An Amniocentesis test is recommended when there is an increased risk of chromosomal or genetic birth defects or certain malformations. Amniocentesis test is usually performed in the second trimester or anywhere between 11 – 14 weeks of pregnancy.


  • Pregnant women who are 35 years or older are offered the option of taking an amniocentesis test to rule out any mental and physical abnormalities. Chances of disorders such as Down syndrome increase to 1 in 400 by age 35, and 1 in 100 at age 40.

  • When there is a family history that may indicate an increased risk of inheriting a genetic disorder, amniocentesis can be offered for prenatal testing.

  • If there is a previous child or pregnancy with a birth defect, an amniocentesis test can help diagnose any chromosomal abnormality.

  • If you have a blood sensitization such as Rh sensitization, an amniocentesis test can help determine if your blood type is different from that of your baby.


Most chromosomal disorders such as Down syndrome and Edward’s syndrome can be detected with the help of an amniocentesis test. It is also possible to diagnose conditions such as cystic fibrosis, sickle cell disease, Huntington’s disease and Tay-Sachs disease. Neural tube defects such as spina bifida and anencephaly can be detected with an amniocentesis test. However, no one prenatal test can guarantee the birth of a healthy baby, since only some birth defects can be ruled out before birth. Amniocentesis test has an accuracy rate of between 99.4 and 100 % in diagnosing chromosomal abnormalities. Other reasons for suggesting an amniocentesis test:


  • To determine whether the fetal lungs are mature for early delivery, in case circumstances demand it
  • An amniocentesis test can diagnose uterine infections
  • Amniocentesis can help in determining the severity of fetal anemia in cases of Rh disease


Amniocentesis Procedure


This procedure takes about 20 minutes. The technician uses an ultrasound to detect a pocket of amniotic fluid that is a safe distance from the baby and placenta. A long, thin and hollow needle is inserted through the abdominal wall into the amniotic fluid. A small amount of amniotic fluid is drawn out for testing. While some women experience cramping or pinching, others feel no discomfort at all. It is advisable to take it easy for a day and avoid heavy work.

Some women notice spotting or leaking amniotic fluid. After the sample is taken, the physician uses ultrasound to check that the fetal heartbeat is normal. The amniotic fluid drawn during the test is tested in a laboratory for chromosomal abnormalities and genetic birth defects. The amniotic fluid contains numerous free-floating fetal cells that can be grown in a laboratory. When these cells multiply and reach a certain number, their chromosomes or genes are extracted and analyzed. It takes nearly 3 weeks to procure the results from an amniocentesis test.


Risk of Amniocentesis

According to the Centers for Disease Control and Prevention (CDC), the rate of miscarriage with amniocentesis is between one in 400 and one in 200 procedures. First-trimester amniocentesis carries more risk than second-trimester amniocentesis. There is a slight risk of developing an uterine infection in the days following the procedure. It is therefore essential to get the amniocentesis test done under an experienced doctor. Knowing about your child’s condition can help you prepare for challenges that you may have to face. With continuous ultrasound guidance is used, injuries to the baby from the amniocentesis needle are very rare. The amniocentesis needle is guided into the sac with the help of ultrasound imaging. Once the needle is in the sac, a syringe is used to withdraw the clear amber-colored amniotic fluid. The volume of fluid withdrawn depends upon the age of the fetus and the reason for the testing.


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Amniocentesis