Amniocentesis, performed between the 16th but before the 20th week of pregnancy, helps detect chromosomal disorders in the foetus. KK Women's and Children's Hospital (KKH) explains.
Amniocentesis is a procedure where an obstetrician withdraws a small amount of the amniotic fluid (about 20cc) surrounding the foetus.
This is done by inserting a thin hollow needle through the mother's abdomen into the uterus.
The obstetrician will use ultrasound to guide the needle during the procedure so as not to harm the unborn child.
The procedure is performed on an outpatient basis and takes only a few minutes.
The needle will cause some pain when it penetrates the uterus, but the pain should not last long and should not hurt more than an injection into any other part of the body.
After the fluid has been withdrawn, the removal of the needle should cause no further discomfort. The fluid is then sent to the laboratory for special tests.
Why is Amniocentesis necessary?
The majority of amniocentesis is done for the detection of chromosomal disorders.
Chromosomes carry genes that pass certain characteristics from parents to their children. When there are too many or too few chromosomes, or there is defect in a chromosome, birth defects usually occur.
Down Syndrome is the most common chromosomal disorder. It causes mental retardation and other health problems such as heart defects. Other less common chromosomal disorders may lead to serious handicaps and death.
When is Amniocentesis done?
Amniocentesis is usually done between 16th week but before the 20th week of pregnancy.
When will the Amniocentesis test results be available?
Usually it takes about 3 to 4 weeks to complete the laboratory tests.
Can all birth defects be detected by Amniocentesis?
No. Amniocentesis can detect almost all known chromosomal disorders. However, birth defects not due to chromosomal abnormalities cannot be detected through this test.
Who should consider Amniocentesis?
Women who are 35 years of age or older at delivery. This is because their children are at an increased risk of chromosomal disorders such as Down Syndrome.
Women who have had a child with Down Syndrome or other chromosomal disorders.
Women who know that they or the baby's father have an unusual chromosome arrangement.
There may be other reasons that apply uniquely to you. Both you and your obstetrician should decide together if you need an amniocentesis.
Is Amniocentesis safe?
Amniocentesis is a safe, low risk procedure when done by experienced medical experts. The risk of miscarriage following the test is reported to be 0.3 to 0.5%.
Useful information
You should be able to return to your normal activities within a few hours after the procedure.
You may have your bath as usual.
There are no dietary restrictions relating to this procedure.
No medication is required following this procedure.
Return to the hospital or call your obstetrician if (after an Amniocentesis):
- You run a fever
- You feel nauseated and vomit
- You experience pain in the shoulder
- You experience any unusual lower abdominal pain
- You notice vaginal bleeding
- You notice leakage of fluid from the vagina
Ref: M19
