Amniocentesis: what it is and when to do it

Amniocentesis: what it is and when to do it


THE amniocentesis is a common prenatal examination used to diagnose certain malformations and genetic disorders of the baby. Amniocentesis consists of introducing a needle through the abdominal wall and uterus to the amniotic cavity where the fetus is located to remove a small amount of amniotic fluid.

  • When to do amniocentesis

  • Why amniocentesis is performed

  • Indications of amniocentesis

  • Risks of Down Syndrome

When to do amniocentesis

The amniocentesis procedure is usually done between the 16th and 18th week gestation.

Why amniocentesis is performed

Amniocentesis serves to know the number of chromosomes in the fetus and to detect possible abnormalities in the fetus. The most commonly sought syndrome is Down syndrome. On the other hand, the exam is not able to determine malformations in the organs and mental retardation.

Indications of amniocentesis

The main indication for performing amniocentesis is pregnant age. The older the woman, the greater the risk that the fetus will suffer from some change in its chromosomes, especially Down’s Syndrome.

Risks of Down Syndrome

In pregnant women up to 25 years old, the risk is 1 in 1,250. This rate rises to 1 in 274 for pregnant women under 35 and reaches 1 in 79 in women over 40. Because of this, many countries adopt the age of 35 years as a basis for indicating amniocentesis. In addition, anyone who has children with chromosomal changes or when a parent has any of these changes should also be tested.

Photo: © Valentina Razumova –

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