Amniocentesis

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Amniocentesis (also referred to as amniotic fluid test or AFT), is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections ^[1], 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.

Contents 1 Procedure 2 Risks and Drawbacks 3 Amniocentesis and stem cells 4 See also 5 References 6 External Links

[edit] Procedure

Before the start of the procedure, a local anesthetic can be given to the mother in order to relieve the pain felt during the insertion of the needle used to withdraw the fluid. After the local is in effect, a needle is usually inserted through the mother's abdominal wall, then through the wall of the uterus, and finally into the amniotic sac. With the aid of ultrasound-guidance, a physician punctures the sac in an area away from the fetus and extracts approximately 20 ml of amniotic fluid. After the amniotic fluid is extracted, the fetal cells are separated from the sample. 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 [Trisomy 18] and Turner syndrome [Monosomy X]. In regards to the fetus, the puncture heals and the amniotic sac replenishes the liquid over the next 24-48 hours.

[edit] Risks and Drawbacks

Amniocentesis is performed between the 16th-20th week of pregnancy; performing this test early can lead to injury to the baby's limbs. 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 1970s originally estimated the risk of amniocentesis-related miscarriage at around 1 in 200 (0.5%).^[2] A more recent study (2006) has indicated this may actually be much lower, perhaps as low as 1 in 1,600 (0.06%).^[2] 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 ^[3].

One simple drawback is that administration may be painful.

[edit] Amniocentesis and stem cells

Recent studies have discovered that amniotic fluid can be a rich source of multipotent mesenchymal, hematopoietic, neural, epithelial and endothelial stem cells.^[4][5][1]. A 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.

Artificial heart valves, working tracheas, as well as muscle, fat, bone, heart, neural and liver cells have all been engineered through use of amniotic stem cells.^[6] Tissues obtained from amniotic cell lines show promise for patients suffering from congenital diseases/malformations of the heart, liver, lungs, kidneys, and cerebral tissue [2].

The first amniotic stem cells bank in US is active in Boston, Massachussets [3] [4] [5].

[edit] See also

• Chorionic villus sampling
• Percutaneous umbilical cord blood sampling
• Prenatal diagnosis
• Amniotic stem cells
• Amniotic fluid

[edit] References

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Usually genetic counseling is offered prior to amniocentesis.

[edit] External Links

Amniodex is an interactive decision support intervention designed for women faced with the decision of whether to undergo amniocentesis.