Amniocentesis in pregnancy: risks and benefits


Amniocentesis in pregnancy is a special test that can reveal important features about baby’s development in uterus. Amniocentesis is the name given to the procedure that withdraws this amniotic fluid from the uterus.  Amniotic fluid contains cells from the baby’s skin and other organs, which can be used to diagnose his condition. Here you will foud out when why and how is done this test. And also which are the benefits and the risks of this special test in pregnancy.

Why amniocentesis is done in pregnancy?

You will probably want to have amniocentesis if you are over the age of 37, as the risk of chromosomal abnormalities such as Down’s syndrome) increases with age. It may also be suggested after serum screening (Bart’s triple test), or if nuchal scan shows a risk of Down’s syndrome. Amniocentesis can also reveal other important information, which may be sometimes helpful in determining the care and progress of your pregnancy.

At one time amniocentesis was used to check for metabolic disorders, but most of these are now diagnosed by CVS (chorionic villus sampling). It was also used to check the bilirubin content of the fluid to help work out if a Rhesus- positive baby needed a blood transfusion while still in the mother’s uterus, but this is now done by a Doppler scan to check for fetal anemia.

What amniocentesis in pregnancy can reveal?

Where there is cause for concern, an amniocentesis test may show the following:

  • The sex of the baby: cells sloughed off by the fetus accumulate in the amniotic fluid. Under the microscope, male cells can be distinguished from female cells and the baby’s sex determined. In gender- linked genetically linked disorders such as hemophilia, a male child will have a 50 per cent chance of being affected
  • The chemical composition of the fluid: this can reveal metabolic disorders caused by missing or defective enzymes
  • The chromosome count: determined by examining discarded cells. Any deviations from the normal chromosomal structure usually mean that the baby may have a disability.

How is amniocentesis done?

Amniocentesis is usually carried out at 16-18 weeks. Guided by ultrasound, the doctor inserts a hollow needle into the amniotic sac through the front of the abdominal wall. About 14 grams (half an ounce) of amniotic fluid is usually with-drawn and this is then spun in a centrifuge to separate the cells shed by the baby from the rest of the liquid. The cells then have to be cultured and it takes about three weeks for the results to come through- a very stressful period for couple. Many women talk about putting their pregnancies ‘’ on hold’’ during this time, until the results confirm that the baby is unaffected.


Amniocentesis is only undertaken with ultrasound monitoring to guide the needle into the amniotic sac, so that neither the placenta nor the fetus is harmed. The risk of the procedure inducing miscarriage in early pregnancy is small- about one in 200. There is also a possibility of a very small risk less than one per cent) of respiratory difficulties in babies after amniocentesis.