Extended cryopreservation and Embryo Transfer
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Extended cryopreservation and embryo transfer refers to a variation in the process of in vitro fertilization (IVF) whereby an embryo is frozen for an extended period of time eventually to be placed into the uterus of a female with the intent to establish a pregnancy. In this case, the embryo is in its blastocyst stage or up to 8 weeks in gestation prior to being frozen. In addition, rather than create the embryo via In vitro fertilization, the embryo may have been produced by natural means, and removed via a specialized embryonic removal procedure.
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[edit] Procedure
The extended cryopreservation procedure is very similar to typical embryo transfer. It starts by placing a speculum in the vagina to visualize the cervix, which is cleansed with saline solution or culture media. A transfer catheter is loaded with the embryos and handed to the clinician after confirmation of the patient’s identity. The catheter is inserted through the cervical canal and advanced into the uterine cavity, where the embryos are deposited. The catheter is then withdrawn and handed to the embryologist, who inspects it for retained embryos. An abdominal ultrasound is often used to ensure correct placement, which is 1-2 cm from the uterine fundus. Anesthesia is generally not required.
Single embryo transfers in particular require accuracy and precision in placement within the uterine cavity. The optimal target for embryo placement, known as the maximal implantation potential (MIP) point, is identified using 3D/4D ultrasound.
[edit] Third-party reproduction
As with cryopreservation and embryo transfer, it is not necessary that the embryo transfer be performed on the female who provided the eggs. Thus another female whose uterus is appropriately prepared can receive the embryo and become pregnant. This is equivalent to surrogate, or gestational carrier, pregnancy. Extended cryopreservation is even more controversial given that the embryo can be more than 6 weeks into its gestation prior to cryopreservation.
[edit] History
The first successful extended cryopreservation was reported in July 1997 and subsequently led to the announcement of the first human birth more than two years later in August 1999. The embryo was 17 days in gestation when it was removed and preserved cryogenically. It was frozen for 2 additional months before being re-implanted into the woman. This procedure was performed under the direction of Dr. Shinji Kayama at Tokyo University.
Dr. Kayama invented the technique from a very personal story. His own sister was diagnosed with breast cancer within days of learning she was pregnant. His sister was forced to abort her pregnancy in order to undergo chemotherapy and treatment for her cancer. As a result of her treatment, his sister was unable to conceive her own children.
Since first reported, Dr. Kayama has worked with a team of researchers in Japan and Sweden to extend both the cryopreservation period and the time during which the procedure may be performed. As of October 2009, more than 3000 embryos have been cryogenically frozen using Dr. Kayama’s techniques, with an average gestation period of 3.5 weeks prior to being frozen. Thus far, 2187 have led to successful births, with the remainder frozen. There have been no cases wherein the embryo did not successfully gestate.
[edit] Controversy
Extended cryopreservation and subsequent embryo transfer remains extremely controversial. It is legal in only five countries: Japan, Iceland, Sweden, Norway, and South Korea. Within the United States, there was a movement for an amendment in the Constitution to ban the procedure, along with human cloning. There have also been isolated cases where the procedure was performed unknowingly to the woman carrying the fetus. These have transpired across the world, including rumors that it has transpired within the United States. In most cases, women seeking an abortion have had the fetus removed via extended cryopreservation. The first and most famous case occurred in 2007 in the United Kingdom. Dr. Lawrence Bittman, an obstetrician at Marie Stopes for 10 years, admitted to performing the procedure at least four times to women unknowingly. Each time the embryo was then successfully implanted into another woman undergoing fertility treatments at the London Fertility Centre. Dr. Bittman presented himself to the authorities and the case is still pending, as there is no legal precedence for this case. At the time of his confession, his collaborator at the Fertility Centre, Dr. Harrison Graham, remains at large. Dr. Bittman has also claimed that he is not the only obstetrician who has done this, and has suggested that there are many physicians across the globe that are illicitly performing the procedure.
[edit] Footnotes
- ^ Gergely RZ, DeUgarte CM, Danzer H, Surrey M, Hill D, DeCherney AH (2005). "Three dimensional/four dimensional ultrasound-guided embryo transfer using the maximal implantation potential point". Fertil. Steril. 84 (2): 500–3. doi:. PMID 16084896..
- ^ http://query.nytimes.com/gst/fullpage.html?sec=health&res=9404EEDC143BF937A35751C0A962948260
- ^ http://www.humc.edu/calendar/careacc.html
- ^ a b http://www.time.com/time/magazine/article/0,9171,952517,00.html
- ^ a b http://www.time.com/time/magazine/article/0,9171,952514,00.html
- ^ http://www.cdc.gov/ART/
- ^ http://www.obgmanagement.com/srm/pdf/first_live_birth_donation.pdf
- ^ http://www.obgmanagement.com/srm.asp?id=5030
- ^ Embryo Transfer in Cattle Retrieved on 21 October 2008
- ^ Embryo Sexing Technology Retrieved on 21 October 2008
[edit] External links
- How embryo transfer works as part of fertility treatment
- The blastocyst transfer process - a form of embryo transfer
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