Amniocentesis (amniotic fluid test)

What is Amniocentesis?

Amniocentesis is a prenatal diagnostic test that involves the withdrawal of amniotic fluid from a woman’s womb for laboratory analysis. The amniotic fluid contains fetal cells and chemical composition that can provide information about the genetic make-up of the fetus. Amniocentesis is typically performed between the 15th and 20th week of pregnancy.

Preparation for Amniocentesis

Before a woman has an amniocentesis procedure, her doctor will discuss the risks and benefits associated with the test. She may be asked to sign a consent form before the procedure is performed. The woman should empty her bladder and bowel and may be asked to lie down on an examination table.

Procedure of Amniocentesis

  • The woman will receive an injection of local anaesthetic.
  • A sample of amniotic fluid will be taken using a needle that is passed through the woman’s abdominal wall.
  • The entire procedure lasts between 10 and 15 minutes.
  • The doctor will then take the needle out.
  • Compresses or a dressing may be applied to the injection site if there is some bleeding.
  • The woman will be asked to rest for a while.

Types of Amniocentesis

  • Diagnostic Amniocentesis: This kind is performed to diagnose certain genetic or chromosomal conditions that can cause birth defects.
  • Fetal Lung Maturity Amniocentesis: This kind of amniocentesis can help determine whether a baby's lungs are mature enough to cope with a normal delivery. It is often used to decide whether early delivery of the baby is advisable.

Why is Amniocentesis carried out?

Amniocentesis is mainly used to check if a baby has any genetic or chromosomal disorders such as Down’s Syndrome or Cystic Fibrosis. It can also be used to check for other conditions such as spina bifida, sickle cell anaemia, thalassaemia and certain neural tube defects. It is also used to check for serious and rare conditions such as Tay-Sachs syndrome and Huntington’s disease.

When is Amniocentesis performed?

Amniocentesis is usually performed between 15 and 20 weeks of pregnancy. It is important to note that if the procedure is done before the 15th week of pregnancy, there is an increased risk of miscarriage.

Risks of Amniocentesis

Amniocentesis is generally a safe procedure, but there are certain risks associated with it such as infection, bleeding or miscarriage, although the latter is rare.