Embryo cryopreservation
Encyclopedia
Cryopreservation
of embryo
s is the process of preserving an embryo at sub-zero temperatures, generally at an embryogenesis
stage corresponding to pre-implantation, that is, from fertilisation
to the blastocyst
stage.
, as patients who fail to conceive may become pregnant using such embryos without having to go through a full IVF cycle. Or, if pregnancy occurred, they could return later for another pregnancy. Spare oocytes or embryos resulting from fertility treatments may be used for oocyte donation or embryo donation to another woman or couple, and embryos may be created, frozen and stored specifically for transfer and donation by using donor eggs and sperm.
(ICSI). Children born from vitrified blastocysts have significantly higher birthweight than those born from non-frozen blastocysts. For early cleavage embryos, frozen ones appear to have at least as good obstetric outcome, measured as preterm birth and low birthweight for children born after cryopreservation as compared with children born after fresh cycles.
Oocyte age, survival proportion, and number of transferred embryos are predictors of pregnancy outcome.
Pregnancies have been reported from embryos stored for 16 years. A study of more than 11,000 cryopreserved human embryos showed no significant effect of storage time on post-thaw survival for IVF or oocyte donation cycles, or for embryos frozen at the pronuclear or cleavage stages. In addition, the duration of storage had no significant effect on clinical pregnancy, miscarriage, implantation, or live birth rate, whether from IVF or oocyte donation cycles.
.
from Kolkata
, India
reported the successful cryopreservation of an eight cell embryo, storing it for 53 days, thawing and replacing it into the mother’s womb, resulting in a successful and live birth as early as 1978- a full five years before Trounson and Mohr had done so. A small publication of Mukherjee in 1978 clearly shows that Mukherjee was on the right line of thinking much before anyone else had demonstrated the successful outcome of a pregnancy following the transfer of a 8-cell frozen-thawed embryo into human subjects transferring 8-cell cryopreserved embryos.” (Current Science, Vol .72. No. 7, 10th april1997)
Cryopreservation
Cryopreservation is a process where cells or whole tissues are preserved by cooling to low sub-zero temperatures, such as 77 K or −196 °C . At these low temperatures, any biological activity, including the biochemical reactions that would lead to cell death, is effectively stopped...
of embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s is the process of preserving an embryo at sub-zero temperatures, generally at an embryogenesis
Embryogenesis
Embryogenesis is the process by which the embryo is formed and develops, until it develops into a fetus.Embryogenesis starts with the fertilization of the ovum by sperm. The fertilized ovum is referred to as a zygote...
stage corresponding to pre-implantation, that is, from fertilisation
Fertilisation
Fertilisation is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo...
to the blastocyst
Blastocyst
The blastocyst is a structure formed in the early embryogenesis of mammals, after the formation of the morula. It is a specifically mammalian example of a blastula. It possesses an inner cell mass , or embryoblast, which subsequently forms the embryo, and an outer layer of cells, or trophoblast,...
stage.
Indications
Embryo cryopreservation is useful for leftover embryos after a cycle of in vitro fertilisationIn vitro fertilisation
In vitro fertilisation is a process by which egg cells are fertilised by sperm outside the body: in vitro. IVF is a major treatment in infertility when other methods of assisted reproductive technology have failed...
, as patients who fail to conceive may become pregnant using such embryos without having to go through a full IVF cycle. Or, if pregnancy occurred, they could return later for another pregnancy. Spare oocytes or embryos resulting from fertility treatments may be used for oocyte donation or embryo donation to another woman or couple, and embryos may be created, frozen and stored specifically for transfer and donation by using donor eggs and sperm.
Prevalence
World usage data is hard to come by but it was reported in a study of 23 countries that almost 42,000 frozen human embryo transfers were performed during 2001 in Europe.Pregnancy outcome and determinants
The outcome from using cryopreserved embryos has uniformly been positive with no increase in birth defects or development abnormalities, also between fresh versus frozen eggs used for intracytoplasmic sperm injectionIntracytoplasmic sperm injection
Intracytoplasmic sperm injection is an in vitro fertilization procedure in which a single sperm is injected directly into an egg.-Indications:...
(ICSI). Children born from vitrified blastocysts have significantly higher birthweight than those born from non-frozen blastocysts. For early cleavage embryos, frozen ones appear to have at least as good obstetric outcome, measured as preterm birth and low birthweight for children born after cryopreservation as compared with children born after fresh cycles.
Oocyte age, survival proportion, and number of transferred embryos are predictors of pregnancy outcome.
Pregnancies have been reported from embryos stored for 16 years. A study of more than 11,000 cryopreserved human embryos showed no significant effect of storage time on post-thaw survival for IVF or oocyte donation cycles, or for embryos frozen at the pronuclear or cleavage stages. In addition, the duration of storage had no significant effect on clinical pregnancy, miscarriage, implantation, or live birth rate, whether from IVF or oocyte donation cycles.
Legislation
From October 1, 2009 human embryos are allowed to be stored for 10 years in the UK, according to the Human Fertilisation and Embryology Act 2008Human Fertilisation and Embryology Act 2008
The Bill's discussion in Parliament did not permit time to debate whether it should extend abortion rights under the Abortion Act 1967 to also cover Northern Ireland...
.
History
The first ever pregnancy derived from a frozen human embryo was reported by Alan Trounson & Linda Mohr in 1983 (although the fetus aborted spontaneously at about 20 weeks of gestation); the first term pregnancies derived from frozen human frozen freezing process was born in 1984. Since then and up to 2008 it is estimated that between 350,000 and half a million IVF babies have been born from embryos frozen at a controlled rate and then stored in liquid nitrogen; additionally a few hundred births have been born from vitrified oocytes but firm figures are hard to come by. It may be noted that Subash MukhopadyaySubhash Mukhopadhyay (physician)
Subhash Mukhopadhyay was a physician from Kolkata, India.-Early life:He was born on January 16, 1931 in Hazaribag, Bihar , India. He studied and graduated with an honours degree in physiology from the Calcutta National Medical College, which was then affiliated with the prestigious University...
from Kolkata
Kolkata
Kolkata , formerly known as Calcutta, is the capital of the Indian state of West Bengal. Located on the east bank of the Hooghly River, it was the commercial capital of East India...
, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
reported the successful cryopreservation of an eight cell embryo, storing it for 53 days, thawing and replacing it into the mother’s womb, resulting in a successful and live birth as early as 1978- a full five years before Trounson and Mohr had done so. A small publication of Mukherjee in 1978 clearly shows that Mukherjee was on the right line of thinking much before anyone else had demonstrated the successful outcome of a pregnancy following the transfer of a 8-cell frozen-thawed embryo into human subjects transferring 8-cell cryopreserved embryos.” (Current Science, Vol .72. No. 7, 10th april1997)