amniocentesis


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amniocentesis

amniocentesis (ămˌnēōˌsĕntēˈsĭs), 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 pregnancy). The procedure can be done in a hospital or in a doctor's office. Ultrasound 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 syndrome, Tay-Sachs disease) 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 palate.

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 abortion is still an option. It can also be used in the third trimester (after 30 weeks) when Rh incompatibility (see erythroblastosis fetalis) 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 defects; chorionic villus sampling; embryo screening.

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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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
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.