amniocentesis


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amniocentesis

(ăm'nēō'sĕntē`sĭs), diagnostic procedure in which a sample of the amniotic fluid surrounding a fetus is removed from the uterus by means of a fine needle inserted through the abdomen of the pregnant woman (see pregnancypregnancy,
period of time between fertilization of the ovum (conception) and birth, during which mammals carry their developing young in the uterus (see embryo). The average duration of pregnancy in humans is about 280 days, equal to 9 calendar months.
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). The procedure can be done in a hospital or in a doctor's office. Ultrasoundultrasound
or sonography,
in medicine, technique that uses sound waves to study and treat hard-to-reach body areas. In scanning with ultrasound, high-frequency sound waves are transmitted to the area of interest and the returning echoes recorded (for more detail, see
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 is used to determine the location of the fetus during the procedure. Fetal cells in the fluid can be grown in the laboratory and studied to detect the presence of certain genetic disorders (e.g., Down syndromeDown syndrome,
congenital disorder characterized by mild to severe mental retardation, slow physical development, and characteristic physical features. Down syndrome affects about 1 in every 730 live births and occurs in all populations equally.
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, Tay-Sachs diseaseTay-Sachs disease
, rare hereditary disease caused by a genetic mutation that leaves the body unable to produce an enzyme necessary for fat metabolism in nerve cells, producing central nervous system degeneration.
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) or physical abnormalities (e.g., anencephaly, or incomplete development of the brain). The sample also can be examined to determine the gender of the fetus and has been used to preselect the sex of the baby, a practice that, although controversial, is much used in some parts of the world. Amniocentesis cannot be used to detect such defects as congenital heart disease or cleft palatecleft palate,
incomplete fusion of bones of the palate. The cleft may be confined to the soft palate at the back of the mouth; it may include the hard palate, or roof of the mouth; or it may extend through the gum and lip, producing a gap in the teeth and a cleft lip, which is
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.

Amniocentesis is generally recommended when there is a family history of genetic disorders or when the woman is over age 35 and therefore at a higher risk of having a baby with a chromosomal abnormality. The procedure is usually carried out around the 14th or 15th week of pregnancy, when there is sufficient amniotic fluid and abortionabortion,
expulsion of the products of conception before the embryo or fetus is viable. Any interruption of human pregnancy prior to the 28th week is known as abortion. The term spontaneous abortion, or miscarriage, is used to signify delivery of a nonviable embryo or fetus due
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 is still an option. It can also be used in the third trimester (after 30 weeks) when Rh incompatibility (see erythroblastosis fetaliserythroblastosis fetalis
, hemolytic disease of a newborn infant caused by blood group incompatibility between mother and child. Although the Rh factor is responsible for the most severe cases of erythroblastosis fetalis, the disease may be produced by any of the other blood
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) is suspected, or to determine the status of the fetus in early or late delivery or when there are signs of fetal distress.

See also birth defectsbirth defects,
abnormalities in physical or mental structure or function that are present at birth. They range from minor to seriously deforming or life-threatening. A major defect of some type occurs in approximately 3% of all births.
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; chorionic villus samplingchorionic villus sampling
(CVS) or chorionic villus biopsy
(CVB) , diagnostic procedure in which a sample of chorionic villi from the developing placenta is removed from the uterus of a pregnant woman (see pregnancy) using a fine needle inserted through the abdomen or
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; embryo screeningembryo screening,
procedure (see genetic testing) in which a single cell is removed from an embryo two or three days after it has been conceived through in vitro fertilization and tested for genetic abnormalities.
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.

amniocentesis

[¦am·nē·ō‚sen′tē·səs]
(medicine)
A procedure during pregnancy by which the abdominal wall and fetal membranes are punctured with a cannula to withdraw amniotic fluid.
References in periodicals archive ?
Increasing demand for conducting biochemical and cytogenetic research studies is further expected to contribute towards growth of the global amniocentesis needle market.
Igualmente reportan la relacion entre la presencia de manchado y perdida de liquido amniotico despues de la amniocentesis y la incidencia de aborto espontaneo.
The mean and standard deviation of maternal characteristics including age and gestational age of amniocentesis and distribution of smoking prevalence did not differ markedly between the case and control groups (Table 1).
Results: Amniocentesis does not cause any significant changes in fetal ductus venosus Doppler waveforms.
Dr Bryan Beattie, a consultant in obstetrics and fetal medicine, said there is about a 1% risk that amniocentesis can cause miscarriage.
But it identifies fewer chromosomal abnormalities than combination screening or the more invasive chorionic villus sampling and amniocentesis. If cf-DNA comes back positive, you generally have the finding confirmed by an invasive test.
Amniocentesis and chorionic villus sampling (CVS) are common prenatal tests used to detect fetal genetic mutations; they analyze fluid or cells extracted from the amniotic sac using a needle that placed through either the abdomen or vagina.
Amniocentesis is generally performed under real-time ultrasonography during the second trimester, when the fetus occupies approximately half of the amniotic cavity and the ratio of viable to nonviable cells in the amniotic fluid is greatest.
(1.) Encyclopedia of Surgery: Amniocentesis. http://www.surgeryencyclopedia.com/A-Ce/Amniocentesis.html.
The researchers from the Imperial College London used stem cells from amniotic fluid donated by mothers undergoing amniocentesis for other purposes during the first trimester of pregnancy.
Methods: We analysed cases of all pregnant women who underwent Amniocentesis at the Foetal Medicine Unit of Aga Khan University Hospital, Karachi, during 2001 to 2010.
(4) The Royal College of Obstetricians and Gynaecologists guideline on amniocentesis and chorionic villus sampling advises that patients should be informed of an additional 1% risk of fetal loss following an amniocentesis, and a slightly higher risk following chorionic villus sampling.