Amniocentesis (also referred to as amniotic fluid test or AFT), is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections , in which a small amount of amniotic fluid, which contains fetal tissues, is extracted from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for genetic abnormalities.

Procedure

Before the actual procedure, a local anesthetic is sometimes given to relieve the pain when inserting the needle used to withdraw the fluid. A needle is usually inserted through the mother's abdominal wall through the wall of the uterus into the amniotic sac. With the aid of ultrasound-guidance, a physician aims towards an area of the sac that is away from the fetus and extracts approximately 20ml of amniotic fluid for testing. The puncture heals, and the amniotic sac replenishes the liquid over a day or so. After the amniotic fluid is extracted, the fetal cells are separated from it. The cells are grown in a culture medium, then fixed and stained. Under a microscope the chromosomes are examined for abnormalities. The most common abnormalities detected are Down syndrome, Edward syndrome 18 and Turner syndrome X. Amniocentesis is most safely performed after the 14th-16th week of pregnancy, but can be done as early as 10th week. Usually genetic counseling is offered prior to amniocentesis.

Risks

Although the procedure is routine, possible complications include infection of the amniotic sac from the needle, and failure of the puncture to heal properly, which can result in leakage or infection. Serious complications can result in miscarriage. Other possible complications include preterm labor and delivery, respiratory distress, postural deformities, fetal trauma and alloimmunisation (rhesus disease). Studies from the 1970's originally estimated the risk of amniocentesis-related miscarriage at around 1 in 200 (0.5%).[http://www.webmd.com/content/article/129/117333.htm Amniocentesis Risk Overrated? ] A more recent study (2006) has indicated this may actually be much lower, perhaps as low as 1 in 1,600 (0.06%). In contrast, the risk of miscarriage from chorionic villus sampling (CVS) is believed to be approximately 1 in 100, although CVS may be done up to four weeks earlier, and may be preferable if the possibility of genetic defects is thought to be higher .

Amniocentesis and stem cells

Recent studies discovered that in amniotic fluid there are a lot of multipotent stem cell, mesenchimal, ematopoietich, neural and epitelial stem cell123. Amniotic stem cells don't have ethical problem. In fact, in harvesting embryonic stem cells, a human embryo is destroyed, and so it's considered it immoral. Another potential benefit of using amniotic stem cells over those obtained from embryos is that they side-step ethical concerns among pro-life activists by obtaining pluripotent lines of undifferentiated cells without harm to a fetus or destruction of an embryo.