Intrauterine insemination has been carried out for many years and the recent European Society of Human Reproduction and Embryology showed a consistent increase throughout the years reaching in excess of 150,000 IUI cycles in heterosexual couples while close to 30,000 IUI cycles in donor cycles.
Although it is a well-known fact that in IVF cycles progesterone had a significant increase chance of success, whether progesterone used in IUI would be beneficial. In the analysis done, produced a general of assisted reproduction and genetics in 2014, the observers Miral Beix demonstrated that when the luteal phase was supplemented with vaginal progesterone, this significantly increases the live birth rate in women undergoing intrauterine insemination only when they were stimulated with Gonadotrophins (FSH/LH)
On the other hand, when women where Clomiphene was used to stimulate the ovaries, progesterone supplementation did not increase the success rate.
Although this is a small trial, this does give some important understanding into how, even in intrauterine insemination cycles, when stimulation with Gonadotropins takes place, it may be beneficial to use progesterone. These trials have been small and we need further larger studies to be able to convince us about this treatment.