Amniocentesis identifies and diagnoses genetic and chromosomal abnormalities, such as certain chromosomal diseases, especially Down syndrome.

Amniocentesis is performed under the guidance of ultrasound to check the position of the baby and placenta. A fine needle is inserted through the abdominal wall and uterus into the amniotic fluid that surrounds the baby.

The most common reasons for amniocentesis

  • The most common reason for amniocentesis is to check for Down's Syndrome. The risk is related to the age of the mother, for example a mother aged 30 has a 1 in 800 chance and a women aged 45 and over has a 1 in 50. Therefore, when the results of the mothers blood test show a high risk of possible Down syndrome along with abnormal measurements of the fetuses neck done by ultrasound, amniocentesis is recommended.
  • A family history of inherited diseases, (certain myopathies, cystic fibrosis, etc..) metabolic disorders, neural tube defects and chromosomal abnormalities.
  • Older siblings with an existing history of chromosomal disorders
  • When defects, abnormalities and delayed growth are detected during an ultrasound examination.

Down syndrome does not affect only older women: all women are affected even if the risk increases with age.

Knowing the risks of an amniocentesis

  • The risks of amniocentesis to the mother are minimal (less than 1:10,000)
  • Risks to the fetus are rare and there is no impact on the long-term development of the child
  • The risk of miscarriage in the two weeks following amniocentesis, are relatively low, between 0.5% and 1% for a baby and 3% for multiple births
  • The risks of infection should also be taken into account: Severe sepsis is likely to be less than 1 in 1000.

Although amniocentesis is exact in detecting many abnormalities, no test is 100% accurate and some abnormalities may remain undetected.

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