Assisted conception. I—General principlesBMJ 2003; 327 doi: https://doi.org/10.1136/bmj.327.7418.799 (Published 02 October 2003) Cite this as: BMJ 2003;327:799
- Paula Rowell, senior embryologist,
- Peter Braude
- Guy's and St Thomas's assisted conception unit, London
Although many assisted conception technologies exist—and have a bewildering array of acronyms—their principal aim is similar. They all aim to bring sperm and the egg close to each other to promote the chances of fertilisation and, ultimately, achieve a pregnancy.
The three main types of assisted conception are intrauterine insemination, in vitro fertilisation, and intracytoplasmic sperm injection.
Intrauterine insemination—Prepared sperm are deposited in the uterus at a time when ovulation is likely or assisted
In vitro fertilisation—Fertilisation is aided by mixing eggs and sperm in the laboratory
Intracytoplasmic sperm injection—A single sperm is injected directly into the egg cytoplasm to achieve fertilisation.
Each of these assisted conception techniques requires three procedures: pharmacological stimulation of the ovary to promote the production of more than one egg (superovulation); laboratory preparation of the semen sample to yield a highly motile, morphologically normal population of sperm for insemination or injection (sperm preparation); and techniques to aid the union of sperm and egg (assisted fertilisation).
Multifollicular development can be achieved by using oral antioestrogens, such as clomifene citrate or tamoxifen. However, more often multifollicular development requires injected preparations containing the pituitary hormone, follicle stimulating hormone (FSH).
FSH used to be obtained from extracts of urine collected from postmenopausal women, which were then purified to various degrees to remove contaminating proteins and luteinising hormone. The extracts provided a preparation of human menopausal gonadotrophins marketed as human menotropins—for example, Merional, Menogon, Menopur. Variation within batches of gonadotrophins, and the increasing unacceptability of injecting biologically derived substances, has led to the more widespread use of recombinant products. These include Gonal-F (follitropin α) and Puregon (follitropin β). Although chemically pure, and …