Extracorporeal fertilization and embryo transfer.

IVF may be used for diagnostic or therapeutic reasons. In patients with idiopathic infertility IVF may distinguish between defects in the spermatozoa or oocyte. At present IVF and ET offers patients with either tubal or idiopathic infertility only a small chance of becoming pregnant (4 to 13 per cent). General application of IVF and ET will be determined by future success rates and incidence of fetal malformation. Selection, preparation and management of patients requires a specialized team, meticulous attention to detail and intense work. The results at four steps in the procedure can be analysed: the rate of oocyte collection is 85 to 90 per cent, the rate of fertilization, 80 to 90 per cent, the rate of embryo development, 50 to 70 per cent, and the pregnancy rate per laparoscopy, 4 to 13 per cent. The factors determining success are not known. The collection of mature oocytes, the use of particular culture media and ease of embryo transfer are important. There are advantages in using clomiphene citrate HCG stimulation rather than the natural cycle. Pregnancy has occurred despite factors thought to be deleterious to IVF: general anaesthesia, carbon dioxide pneumoperitoneum, prolonged anaesthesia before oocyte collection and bleeding before or after ET. Ethical and legal aspects of IVF and ET require consideration by the community, legal profession and religious groups, and suitable guidelines need to be established for scientists and doctors.