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Amniocentesis

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Amniocentesis
ICD-9-CM75.1
MeSHD000649

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.

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 (trisomy 21), Edwards syndrome (trisomy 18), and Turner syndrome (monosomy X). In regard to the fetus, the puncture heals and the amniotic sac replenishes the liquid over the next 24–48 hours.

Indications and results

Early in pregnancy, used for diagnosis of chromosomal and other fetal problems such as:

Later on, it also can be used to detect problems such as:

  • Infection
  • Rh incompatibility
  • Prediction of lung maturity
  • Decompression of polyhydramnios

An emerging indication for amniocentesis is in the management of preterm rupture of membranes where measurement of certain amniotic fluid inflammatory markers may be helpful. If amniotic fluid IL-6, a marker of inflammation, is elevated, the fetus is at high risk and delivery should be considered.[3]

Risks and drawbacks

Amniocentesis is performed between the 15th-20th week of pregnancy; performing this test early can lead to injury to the baby's limbs. Most people do the test during the 18th week of pregnancy. The term "early amniocentesis" is sometimes used to describe use of the process between weeks 11 and 13.[4]

Serious complications can result in miscarriage. Other possible complications include preterm labor and delivery, respiratory distress, postural deformities, fetal trauma and alloimmunisation of the mother (rhesus disease). Studies from the 1970s originally estimated the risk of amniocentesis-related miscarriage at around 1 in 200 (0.5%).[5] A more recent study (2006) has indicated this may actually be much lower, perhaps as low as 1 in 1,600 (0.06%).[6] 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.[7]

Amniotic fluid embolism has been described as a possible risk.[8]

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.[9][10][11]

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.[12] Tissues obtained from amniotic cell lines show promise for patients suffering from congenital diseases/malformations of the heart, liver, lungs, kidneys, and cerebral tissue.[13]

The first amniotic stem cells bank in US is active in Boston, Massachusetts.[14][15][16][17]

See also

References

  1. ^ "Diagnostic Tests - Amniocentesis". Harvard Medical School. Retrieved 2008-07-15.
  2. ^ Dungan, Jeffrey S. (November 2008). "Prenatal Diagnostic Testing". The Merck Manuals Online Medical Library. Retrieved July 30, 2010. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1017/S096553951000001X, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1017/S096553951000001X instead.
  4. ^ Sundberg K, Bang J, Smidt-Jensen S; et al. (1997). "Randomised study of risk of fetal loss related to early amniocentesis versus chorionic villus sampling". Lancet. 350 (9079): 697–703. doi:10.1016/S0140-6736(97)02449-5. PMID 9291904. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  5. ^ Amniocentesis Risk Overrated?
  6. ^ Eddleman KA, Malone FD, Sullivan L; et al. (2006). "Pregnancy loss rates after midtrimester amniocentesis". Obstet Gynecol. 108 (5): 1067–72. doi:10.1097/01.AOG.0000240135.13594.07. PMID 17077226. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  7. ^ NEJM - The safety and efficacy of chorionic villus sampling for early prenatal diagnosis of cytogenetic abnormalities
  8. ^ Dodgson J, Martin J, Boswell J, Goodall HB, Smith R (1987). "Probable amniotic fluid embolism precipitated by amniocentesis and treated by exchange transfusion". Br Med J (Clin Res Ed). 294 (6583): 1322–3. doi:10.1136/bmj.294.6583.1322. PMC 1246486. PMID 3109636. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  9. ^ Weiss, Rick (2007-01-08). "Scientists See Potential In Amniotic Stem Cells". The Washington Post. Retrieved 2010-04-23.
  10. ^ "Isolation of amniotic stem cell lines with potential for therapy".
  11. ^ "Stem Cells - BiocellCenter". Retrieved 2010-01-11.
  12. ^ "ITALY - Stem cells from amniotic liquid, new hopes".
  13. ^ "Stem cells scientific updates - BiocellCenter". Retrieved 2010-01-11.
  14. ^ "European Biotech Company Biocell Center Opens First U.S. Facility for Preservation of Amniotic Stem Cells in Medford, Massachusetts | Reuters". 2009-10-22. Retrieved 2010-01-11.
  15. ^ "Europe's Biocell Center opens Medford office - Daily Business Update - The Boston Globe". 2009-10-22. Retrieved 2010-01-11.
  16. ^ "The Ticker - BostonHerald.com". Retrieved 2010-01-11.
  17. ^ "Biocell partner with largest New England's hospital group to preserve amniotic stem cell". Retrieved 2010-03-10.
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