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Encyclopedia > Amniocentesis

Amniocentesis (also referred to as amniotic fluid test or AFT), is a medical procedure used in prenatal diagnosis of genetic risk factors, 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. Amniocentesis is not performed for every pregnancy, but is generally done when an increased risk of genetic defects in the fetus is indicated, by mother's age (over 35 years is common), family history of genetic defects, or other factors. For the chemical substances known as medicines, see medication. ... Prenatal diagnosis is the diagnosis of disease or condition in a fetus or embryo before it is born. ... For the alien race in Stephen Donaldsons The Gap Cycle, see Amnion (Gap Cycle). ... For other uses, see Fetus (disambiguation). ...

Contents

Procedure

A syringe is usually inserted through the mother's abdominal wall or at the end of the vagina, and through the wall of the uterus into the amniotic sac. With assistance from ultrasound a physician aims an area of the sac that is away from the fetus and extracts a small amount of amniotic fluid for testing. The puncture heals, and the amniotic sac automatically replenishes the liquid over a day or so. After the amniotic fluid is extracted, the fetal cells are separated from it using a centrifuge, and cell chromosomes are examined for abnormalities. Various genetic testing may be performed, but the three most common abnormalities tested for are Down's syndrome, Trisomy 18 and spina bifida. Amniocentesis can be performed as soon as sufficient amniotic fluid surrounds the fetus to allow a sample to be recovered relatively safely, usually no earlier than the 14th week of pregnancy. Often, genetic counseling is offered in conjunction with amniocentesis. The vagina, (from Latin, literally sheath or scabbard ) is the tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. ... For other uses, see Ultrasound (disambiguation). ... This article is about the scientific device. ... This article is about the biological chromosome. ... Genetic testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a persons ancestry. ... Edwards Syndrome is the second most common trisomy after Downs Syndrome. ... Genetic counseling is the process by which patients or relatives, at risk of an inherited disorder, are advised of the consequences and nature of the disorder, the probability of developing or transmitting it, and the options open to them in management and family planning in order to prevent, avoid or...


In addition to the fetal cells, some tests may examine the amniotic fluid for indications of non-genetic diseases the fetus might have. Levels of chemical substances (such as alpha-fetoprotein) can be measured to detect other health problems such as hydrocephalus. Alpha-fetoprotein (AFP) is a protein that is normally only produced in the foetus during its development. ...


An alternative test to examine the genome of the developing fetus is chorionic villus sampling, or CVS. Chorionic villus sampling (CVS) is a form of prenatal diagnosis to determine genetic abnormalities in the fetus. ...


A side benefit of genetic analysis through amniocentesis or CVS is that the sex of the fetus may be determined with 100% accuracy.


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). The risk of amniocentesis-related miscarriage is generally thought to be 1 in 200, although a recent study has indicated this may actually be much lower, perhaps 1 in 1,600.[1] In contrast, the risk of miscarriage for 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. [2] Rh disease (also Rhesus disease or Morbus haemolyticus neonatorum) is a condition that occurs when an Rh negative mother has given birth to an Rh positive baby and subsequently becomes pregnant with an Rh positive child. ...


See also

Chorionic villus sampling (CVS) is a form of prenatal diagnosis to determine genetic abnormalities in the fetus. ... PUBS redirects here. ...

External links


  Results from FactBites:
 
Amniocentesis: Answers to common questions (1191 words)
Amniocentesis is a prenatal test used to identify various genetic problems or test a baby's lung maturity.
Less often, amniocentesis is used to diagnose uterine infections or Rh incompatibility — an uncommon condition in which a mother's immune system produces antibodies against a specific protein on the surface of the baby's blood cells.
Amniocentesis carries a slight risk of miscarriage, often due to rupture of the amniotic sac.
Amniocentesis - Wikipedia, the free encyclopedia (407 words)
Amniocentesis, or an Amniotic Fluid Test (AFT), is a medical procedure used for prenatal diagnosis, in which a small amount of amniotic fluid is extracted from the amnion around a developing fetus.
Amniocentesis is only half as risky to the child than chorionic villus sampling although villus sampling can be done earlier.
Amniocentesis done in the second trimester is often said to have a risk of fetal death between about 1 in 400 and 1 in 200.
  More results at FactBites »

 
 

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