Advanced ART
Micromanipulation, an extraordinary technique in which not only eggs but individual sperm can be manipulated by the embryologist, makes it possible for a man with a very low sperm count and virtually no active sperm to fertilize his partner's egg. Living proof of the success of this advanced technology are the many thousands of babies conceived by ART who are now alive and well.
Micromanipulation
© DK
Intra-cytoplasmic sperm injection (ICSI) is one technique that uses micromanipulation. A prepared egg is placed under a microscope and injected with an individual sperm. Sperm may be collected by masturbation or from a testis using surgical techniques such as MESA or TESE. Once fertilized, the embryo is incubated and implanted when it's reached two to four cells in size. ICSI may be offered to couples who don't conceive by other methods. The first ICSI pregnancy was in 1988. However, there's some controversy about this technique. For example, there's concern that an egg could be fertilized with a sub-standard sperm, possibly resulting in a damaged or unhealthy child. But although the pregnancy rate with ICSI is not quite as high as with IVF, the babies born so far have been normal, with no chromosomal abnormalities.
Embryo transfer during ART
All forms of IVF involve taking an embryo, usually between two and three days old, from the incubating dish in the laboratory and placing it inside a woman's body. Sadly, two out of three embryo transfers fail to implant. Successful implantation depends on the age of the mother, how receptive her uterus is, and the quality of the embryo. One of the problems with this treatment is that doctors still don't know when is the best time to transfer an embryo. Studies suggest that delaying the transfer of an embryo to the uterus can increase the chances of implantation. But in one study, there was no difference between embryos placed 44 hours after insemination and those that were placed after 68 hours.
Pregnancy rates do increase with the numbers of embryos that are placed, but so does the risk of multiple pregnancies. Twin or triplet pregnancies have a far greater risk of complications, such as miscarriage, prematurity, and possible abnormality, so parents are increasingly advised to have only one embryo transferred.
Cryopreserved embryos during ART
It's possible to thaw cryopreserved (frozen) embryos or eggs from liquid nitrogen (-273°C/-523°F) and transfer them. The embryo is thawed slowly, at a rate of 8°C (17°F) per minute. Not all embryos survive this process in a good enough state to implant. Placement in the womb is done at a point in the menstrual cycle 100 hours after the LH (luteinizing hormone) peak - determined by serial blood tests. Pregnancy rates vary from one in six to one in four.
The future of ART
- superovulation of the ovaries - increasing the number of eggs a woman produces - will probably be achieved
- further studies will be made on embryos before transfer
- more research on implantation of the embryo in the uterus
- more research on male infertility, perhaps as the result of refinement of ICSI or the invention of some other method of sperm treatment
- more investigation into cryopreservation techniques to improve egg-freezing methods and the low pregnancy rate with freeze-thawed embryos
- research into in vitro maturation of eggs.
Posted 16.11.2010
Get more on this subject…
