What is Amniotic Fluid Test (AFT) or Amniocentesis


Do you know the amniocentesis technique and its procedure? In the below article you will find the meaning of amniocentesis, the complete procedure, risks of the technique and disorders for which this technique is used.

Introduction

The developing foetus in the womb of the mother is enclosed in an amniotic cavity surrounded by the foetal membrane called amnion. A saline fluid is filled in the amniotic cavity which is called amniotic fluid. This amniotic fluid contains sloughed cells of the foetus thus the genetic makeup of these cells is the same as of the foetus. The test involving the withdrawal of some of the amniotic fluid that bathes the developing foetus and analyzing the foetal cells and dissolved substances for the presence of the certain genetic disorder is called amniotic fluid test (AFT) or amniocentesis. Thus the amniocentesis is a medical procedure involving the prenatal diagnosis of chromosomal abnormalities and foetal infections.

Procedure of Amniocentesis



Amniocentesis
(Image Courtesy: www.wikipedia.org)

Amniocentesis is usually done at 15-16 weeks of gestation. During amniocentesis, the position of the foetus and placenta is first identified using ultrasound and palpation. After that, skin is prepared with an antiseptic and a local anaesthetic is given. A hypodermic syringe is inserted through the mother's abdominal wall and into the amniotic cavity within the uterus. To ensure the correct position of the syringe, it is better to perform the ultrasound scanning of the entire procedure. Now 15-20 ml of fluid and suspended cells are aspirated for microscopic examination and biochemical testing. After taking out the amniotic fluid, it is centrifuged as a result of which the cells are separated from the fluid. Now the level of alpha-fetoprotein (AFP) is measured in the fluid. Elevated levels of alpha-fetoprotein and acetylcholinesterase may indicate failure of the nervous system to develop properly, as occurs in spina bifida or anencephaly or may be due to other developmental or chromosomal problems. In anencephaly, the membranous skull and the cerebral hemispheres are lacking whereas in spina bifida, the vertebral arch is defective and often the spinous processes are lacking.

The centrifugated cells are grown for 2-4 weeks in a culture medium and the cultured cells are fixed and stained. The microscopic examination of stained cells may reveal chromosomal abnormalities. If required, biochemical, cytogenetic and DNA studies of these cells can also be performed. With the help of aforesaid studies, about 60 types of inborn errors of metabolism can be detected. But mostly the diagnosis of the following chromosomal abnormalities is being done by amniocentesis:
  • Down syndrome or Trisomy 21- Risk of a baby suffering from the disorder is high in pregnant women exceeding 37 years of age.

  • Patau Syndrome or Trisomy 13

  • Edward syndrome or Trisomy 18

  • Turner Syndrome

  • Kleinfelter Syndrome

  • Inherited metabolic disorder

  • Infection

  • Rh incompatibility

  • prediction of lung maturity

  • Management of preterm rupture of membranes for which certain amniotic fluid inflammatory markers are measured. Increased amniotic fluid IL-6 marker indicates a high risk for the foetus.

Drawbacks and risk of Amniocentesis

Amniocentesis should usually be done at 15-20 weeks of gestation. The preterm test may damage the limbs of the developing embryo. Chances of miscarriage may arise on complicacy. Other probable complications are preterm labour and delivery. Respiratory distress , postural deformity, foetal trauma, etc. Besides these, the risk of amniotic fluid embolism is also possible to avoid complicacy, amniotic leakage should be investigated. As a result of modern researches, scientists have reached the conclusion that amniotic fluid can prove to be a good source of multipotent mesenchymal, hematopoietic, neural, epithelial and endothelial stem cells.

Last words

Amniocentesis is greatly misused. People use this technique to find the sex of the child and if they find it to be a female child they undertake abortion even if the child is normal. It is cold-blooded murder of the innocent child.


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