Amniocentesis is a minor surgical procedure that can be done in an outpatient setting. This is commonly requested for pregnant patients who want to screen their fetus for the presence of any aberrant genes that may be present, especially for those parents with a strong family history of a genetic abnormality.

The process of removing a small amount of amniotic fluid for testing is done after an ultrasound is performed. The amniotic fluid is the fluid where the fetus is suspended. It is also essential for the nourishment of the fetus and also cushions them from the unexpected trauma of the external environment.

No sedation is required to perform amniocentesis. A small-caliber needle attached to the syringe is used to puncture the abdomen through the umbilicus and guided by an ultrasound probe. After this, the desired amount of fluid is extracted from the womb.


There are two general types of amniocentesis, and these are:

  • Genetic amniocentesis- As the name suggests, this is done to exclude the paternity of the individual
  • Fetal lung maturity amniocentesis- This is used to assess the readiness of the infant to breathe on its own by measuring the lecithin/sphingomyelin ratio. These two substances are essential in the synthesis of lung surfactant.


Amniocentesis is not routinely done during prenatal visits. However, it is done on one of the following settings:

  • Testing for possible Trisomy 21 of the fetus
  • Assessment of the lung maturity of the fetus. This is primarily done among females with a history of previous miscarriage.
  • Detection of occult or hidden pathology- In cases of incompatibility between the blood type of the mother and the offspring. An antibody is produced, causing it to attack the body of the fetus.
  • Testing for disputed paternity- The DNA is harvested from the amniotic fluid is then matched to the supposed parent of the offspring.


Amniocentesis is used to diagnose the following diseases:

  • Trisomy 21 otherwise known as Down’s syndrome
  • Trisomy 13, also known as Patau’s syndrome- The child presents with severe cognitive impairment and abnormalities in the physical appearance.
  • Trisomy 18, also known as Edward’s syndrome. This condition can be detected early in the intrauterine age. This is characterized by low birth weight and smaller than the period of gestation.
  • Fragile X syndrome- characterized by autism-like features, poor cognition, and physical features such as frontal bossing of the forehead, abnormally large lips, and a prominent mandibular curve.
  • The presence of genetic abnormalities is usually correlated with metabolic disorders.


The results of the amniocentesis can both be pleasant (in cases where there is no genetic abnormality found) or can sometimes be heartbreaking (where the results reveal the presence of any of the symptoms as mentioned earlier). The expectant parents are more often than not obliged to make a decision befitting for the baby. In some countries, termination of pregnancy is done primarily in the setting of a definite syndrome amniocentesis and is accepted in several states.

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