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Louise Brown was 21 in 1999. Since her birth, in vitro fertilisation (IVF) has become a widely used treatment for the subfertile couple. Currently about 1% of births in the United Kingdom follow conceptions in vitro. Certain forms of subfertility, largely those derived from male problems (affecting up to 40% of subfertile couples), cannot be treated by conventional IVF, and the development of intracytoplasmic sperm injection (ICSI) has allowed some of these couples to conceive.
What is ICSI?
ICSI was developed in humans in Belgium in 1992.1 The procedure involves injecting a single sperm into an egg using a micropipette one fourteenth the diameter of a human hair. The spermatozoa can be obtained either after ejaculation or after aspiration (directly) from the testis or epididymis (percutaneous epididymal sperm aspiration). The spermatozoa are prepared by washing away seminal plasma and, where possible, separating the progressive (most) motile sperm from cellular debris. Poorly motile or abnormally shaped sperm are not usually selected for injection, unless no normal appearing sperm are available in the preparation. Progressive motile sperm are slowed down in polyvinylpyrrolidine, which increases viscosity of the medium and permits a better spermatozoon selection. Immobilisation is performed by crushing the tail of the spermatozoon with the injection pipette. This disturbs the membrane potential, appears to improve fertilisation, and prevents the tail of the sperm damaging the ovum cytoskeleton. If apparently normal fertilisation occurs, up to three of the resulting embryos are transferred to the uterus 48 hours after egg collection using a standard procedure in which a fine flexible catheter containing the embryos is passed through the cervix into the uterine cavity, and the embryos are expelled in a minimal quantity of medium.
Use of ICSI
ICSI is a major adjunct to conventional IVF and has been rapidly introduced world wide. More than 100 centres in the …
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