The pregnancy rates for intrauterine insemination (IUI) vary widely, depending mostly on the female partner’s age and the presence or absence of any other infertility factors. In patients younger than 35 years old, an estimated one-third to one-half of patients will achieve pregnancy within 1 to 4 treatments. In patients with unexplained infertility, most studies demonstrate a per-cycle pregnancy rate of 6% for the Clomid/IUI combination and 9% to 12% for the gonadotropin/IUI combination, compared with a spontaneous pregnancy rate of less than 5% per month (see Table 3). Many fertility doctors will try 1 to 4 cycles of Clomid/IUI and then 1 to 4 cycles of gonadotropin/IUI. If pregnancy has not occurred after the fourth treatment, most experts would abandon these treatments and proceed with more aggressive therapy such as in vitro fertilization. The optimal number of IUI treatment cycles should be individually determined by the patient and her infertility specialist.

Some patients develop a seeming resistance to fertility medications, demonstrating reduced responses with repeated stimulations. This problem is especially prevalent in women who are more than 37 years old. Thus, in our opinion, IVF should be considered as a first-line treatment in these patients as opposed to multiple gonadotropin/IUI cycles.

Table 3 Unexplained Infertility Success Rates Per Cycle with Various Treatment Options

Method Pregnancy Rate Percent
Intercourse 4
CC 5.6
CC + IUI 8
FSH 7.7
FSH + IUI 17
In vitro fertilization 21

CC, clomiphene citrate; FSH, follicle-stimulating hormone; IUI, intrauterine insemination.
Source: Adapted from Guzick DS, et al. Efficacy of treatment for unexplained infertility. Fertil Steril 70:207, 1998.