What are amniocentesis, when to do it and possible risks

Amniocentesis is an exam that can be performed during pregnancy, usually from the second trimester of pregnancy, and aims to identify genetic changes in the baby or complications that may happen as a result of the woman’s infection during pregnancy, as in the case of toxoplasmosis, for example.

In this test, a small amount of amniotic fluid is collected, which is a fluid that surrounds and protects the baby during pregnancy and that contains cells and substances released during development. Despite being an important test to identify genetic and congenital alterations, amniocentesis is not a mandatory test in pregnancy, being only indicated when pregnancy is considered at risk or when the baby’s alterations are suspected.

When to do amniocentesis

Amniocentesis is recommended from the second trimester of pregnancy, which corresponds to the period between the 13th and 27th weeks of gestation and is usually performed between the 15th and 18th weeks of pregnancy, before the second trimester there are greater risks for the baby and increased chance of miscarriage.

This examination is performed when, after evaluation and performance of the examinations normally requested by the obstetrician, changes are identified that may represent a risk to the baby. So, to check if the baby’s development is happening as expected or if there are signs of genetic or congenital changes, the doctor may request amniocentesis. The main indications for the exam are:

  • Pregnancy over 35 years old, since from that age onwards, pregnancy is more likely to be considered at risk;
  • Mother or father with genetic problems, such as Down syndrome, or family history of genetic changes;
  • Previous pregnancy of a child with any genetic disease;
  • Infection during pregnancy, mainly rubella, cytomegalovirus or toxoplasmosis, which can be transmitted to the baby during pregnancy.

In addition, amniocentesis can be indicated to check the functioning of the baby’s lungs and thus, to carry out paternity tests even during pregnancy or to treat women who are accumulating a lot of amniotic fluid during pregnancy and, thus, amniocentesis is intended objective to remove excess fluid.

The results of the amniocentesis may take up to 2 weeks to come out, however the time between the exam and the report release may vary according to the purpose of the exam.

How amniocentesis is done

Before amniocentesis is performed, the obstetrician performs an ultrasound to check the baby’s position and the amniotic fluid bag, reducing the risk of injury to the baby. After identification, an anesthetic ointment is placed in the place where the amniotic fluid will be collected.

The doctor then inserts the needle through the skin of the belly and removes a small amount of amniotic fluid, which contains the baby’s cells, antibodies, substances and microorganisms that help to carry out the tests necessary to determine the baby’s health.

The exam lasts only a few minutes and during the procedure the doctor listens to the baby’s heart and performs an ultrasound to assess the woman’s uterus to ensure that there is no harm to the baby.

Possible risks

The risks and complications of amniocentesis are rare, however they can happen when the test is performed in the first trimester of pregnancy, with a greater risk of miscarriage. However, when amniocentesis is performed in trusted clinics and by trained professionals, the risk of the test is very low. Some of the risks and complications that can be related to amniocentesis are:

  • Cramps;
  • Vaginal bleeding;
  • Uterine infection, which can be transmitted to the baby;
  • Baby trauma;
  • Induction of early labor;
  • Rh sensitization, which is when the baby’s blood enters the mother’s bloodstream and, depending on the mother’s Rh, there may be reactions and complications for both the woman and the baby.

Due to these risks, the examination should always be discussed with the obstetrician. Although there are other tests to assess the same type of problems, they usually have a higher risk of miscarriage than amniocentesis. See which tests are indicated in pregnancy.

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