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Amniocentesis and Amniotic Fluid


What is amniocentesis?

Amniocentesis is a prenatal test that allows your doctor to gather information about your baby’s health and development.

How is amniocentesis carried out?

Amniocentesis is carried out by inserting a thin, fine needle through the abdomen and into the amniotic sac that surrounds the foetus.  A small sample of the amniotic fluid is removed for analysis in a laboratory.  The test usually takes about 10 minutes to carry out. An ultrasound is used during the procedure to ensure the needle is a safe distance from the baby it will also be used to check the heartbeat is normal and to see how baby is doing.

What is the amniotic sac and fluid?

The amniotic sac, which is sometimes called membranes surrounds the unborn baby it is filled with amniotic fluid. Amniotic fluid is a colourless fluid that surrounds the baby in your uterus. Amniotic fluid helps to protect and cushion your baby inside the amniotic sac. Amniotic fluid also plays a vital role in the development of internal organs, such as the lungs and kidneys.  Amniotic fluid contains some of your baby’s cells, including stem cells, there is constant research being carried out on the full benefit of these cells in regenerative medicine. When the amniotic sac ruptures before you go into labour it is the amniotic fluid that leaks out (Amniotic Leak), this is more commonly known as ‘waters breaking’.

What is amniotic leak?

Prior to delivery of the baby, your ‘waters break’ this is due to the sac carrying the amniotic fluid breaking, hence the name. The fluid can either gush out but more often its a gradual trickle (leak). It can be difficult even for doctors to tell if you are leaking amniotic fluid or urine.

Why is amniocentesis carried out?

Amniocentesis is usually carried out to determine whether the baby has any genetic or chromosomal abnormalities, such as Down’s syndrome, sickle cell disease or cystic fibrosis. The test may also be carried out to determine whether your babies lungs are mature enough for an early delivery should for any reason you appear to be in premature labour. A premature labour is when you go into labour before the proper time.

When is amniocentesis carried out?

The test is commonly carried out between the 15th and 20th week of pregnancy.

Do I have to have amniocentesis?

No, not all women will have this test as it isn’t a routine test and because it carries a small risk of miscarriage .  You do not have to have the test even if it is recommended to you, discuss the test with your doctor or midwife and about the pros and cons of carrying out the test. The test is usually recommended for women when there is an increased risk of birth defects. Reasons you may be offered amniocentesis are as follows:

  • If you are aged over 35 because the risk of chromosomal disorders increase with age.
  • If you have had a previous child with a birth defect.
  • If you have had a blood test for A.F.P. (Alpha-fetoprotein), which shows abnormal levels of A.F.P. Alpha-fetoprotein is a substance found in the blood and high levels could indicate that you baby has a neural tube defect such as spina bifida.
  • If there is a family history that indicates your child may be at risk of inheriting a genetic disorder.

What happens after amniocentesis?

After the test you will have to rest for a while before being allowed home. 1 to 2% women will experience cramping, vaginal spotting or leaking amniotic fluid. If you experience any of these you should contact your doctor.

When do I get the results?

The results will usually be ready within about 3 weeks, though some results will be available in 3 days. If the test shows your baby has a genetic or chromosomal condition then your doctor will discuss the implications of this with you in great detail. If there is no cure for the condition you have to make the difficult decision as to whether you carry on with the pregnancy or have an abortion.