Amniocentesis is a procedure in which amniotic fluid is removed from the uterus for testing or treatment. Amniotic fluid is the fluid that surrounds and protects a baby during pregnancy. This fluid contains fetal cells and various chemicals produced by the baby.
With genetic amniocentesis, a sample of amniotic fluid is tested for certain chromosome/genetic abnormalities - such as Down syndrome and spina bifida (or the open spinal cord in the baby). Arizona Center for Fertility Studies believes that chromosome/genetic amniocentesis should be offered when the test results may have a significant impact on the management of the pregnancy, or the woman's desire to continue the pregnancy.
With maturity amniocentesis, a sample of amniotic fluid is tested to determine whether the baby's lungs are mature enough for birth.
Amniocentesis is usually done after the 13-15th week of pregnancy, when the two layers of the fetal membranes, the chorion, and amnion, have fused enough to safely withdraw a sample of amniotic fluid. It is rarely done before that because of safety concerns. Under ultrasound guidance, a sterile needle is passed through the abdominal wall and into the amniotic sac. A small amount of fluid, containing the baby's cells, is removed and sent for genetic/chromosome analysis. The results take about 3+ weeks. This makes the decision to terminate the pregnancy even more difficult since the woman is well into the 2nd trimester, and probably, because she had done a reproductive procedure like IUI or IVF, she has had considerable pregnancy symptoms and probably has watched the baby grow on ultrasound.
The following are the most common indications for a woman to consider doing an amniocentesis:
Risks associated with amniocentesis are as follows:
Arizona Center for Fertility Studies recommends that chromosome/genetic amniocentesis should only be offered when the test results may have a significant impact on the management of the pregnancy or the desire to continue the pregnancy. The decision to do an amniocentesis is an extremely important one, especially in reproductive medicine. Because the potential complications of amniocentesis can result in losing a normal pregnancy, and everything that the woman went through to achieve that pregnancy, the risks versus the benefits, needs to be carefully weighed. Arizona Center for Fertility Studies believes, that the decision to terminate a pregnancy secondary to a chromosome abnormality like Downs Syndrome, is an extremely difficult and sometimes emotionally painful one, involving so many emotional, religious, spiritual, psychological, and ethnic aspects. It is a decision that the couple needs to make alone or with family, and the clinic needs to be non-judgmental and support whatever decision they make.
If the AFP and TNL are both normal, there is an 85% chance that the baby is normal and does not have Downs Syndrome. The couple needs to weigh those odds against their risk of having a Downs Syndrome baby and the risk of complications from having the procedure before making their decision.
Graphic representation of the amniocentesis procedure done around 14 weeks under ultrasound guidance. A sterile needle is passed through the abdominal wall into the amniotic sac and a small amount of fluid, containing fetal cells, is removed and sent for chromosome/genetic evaluation.
An alternative to amniocentesis is CVS or chorionic villus sampling. The chorionic villi are tiny finger-shaped growths found in the placenta. The genetic material in chorionic villus cells is the same as that in the baby's cells. During CVS, a sample of the chorionic villus cells is taken for chromosome/genetic evaluation, similar to what is done with the amniotic fluid sample. The main difference between CVS and amniocentesis is that the procedure is generally done late in the first trimester between the 10th to 12th week, and the results are available in 7+ days. This allows the couple to know the health of the baby much sooner and make a decision earlier on whether to continue or end the pregnancy.
The indications and risks of complications are similar to those of amniocentesis and, if the woman decides to have a CVS instead of an amnio, it also has to be done by someone with considerable experience and expertise.
Graphic representation of CVS done under ultrasound guidance. It involves inserting a sterile flexible tube through the vagina and cervix and into the placental tissue removing cells that are genetically/chromosomally similar to the fetus.