that in vitro fertilization should be offered to women with unexplained infertility when they have not conceived after two years of regular unprotected sexual intercourse. IVF avails for embryo transfer of the appropriate number of embryos to give good chances of pregnancy with minimal risk of multiple birth. A review of randomized studies came to the result that IVF in couples with a high chance of natural conception, as compared to IUI/ICI with or without ovarian stimulation, was more effective in three studies and less effective in two studies. There is no evidence for an increased risk of ovarian hyperstimulation syndrome (OHSS) with IVF when compared with ovarian stimulation combined with IUI. Prognosis Prognosis in unexplained infertility depends on many factors, but can roughly be estimated by e.g. the Hunault model, which takes into account female age, duration of infertility/subfertility, infertility/subfertility being primary or secondary, percentage of motile sperm and being referred by a general practitioner or gynecologist. See also Male infertility Female infertility References Infertility