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Unidentified Infertility Factors


Robert W. Rebar

, MD, Western Michigan University Homer Stryker M.D. School of Medicine

Last full review/revision Sep 2020| Content last modified Sep 2020
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Unidentified factors are usually considered the explanation for infertility when semen in the man is normal and when ovulation and fallopian tubes are normal and ovulation is regular in the woman.


  • Controlled ovarian stimulation

  • Sometimes assisted reproductive techniques

When no explanation for infertility is identified, an approach called controlled ovarian stimulation may be used.

Controlled ovarian stimulation may make pregnancy more likely and may help women become pregnant more quickly. This treatment may result in more than one fetus.

Controlled ovarian stimulation involves the following:

  • Women are given a fertility drug (clomiphene), which stimulates several eggs to mature and be released, and human chorionic gonadotropin (hCG), which stimulates ovulation, for up to three menstrual cycles.

  • Semen is placed directly in the uterus to bypass the mucus (intrauterine insemination) within 2 days after treatment with hCG.

If pregnancy does not result after this treatment, one of the following may be done:


Women have the same chance of pregnancy (about 65%) whether unsuccessful treatment with clomiphene plus hCG is followed by stimulation with gonadotropins plus hCG or immediately by in vitro fertilization. However, women become pregnant more quickly and are less likely to have a pregnancy with three or more fetuses when unsuccessful treatment with clomiphene is immediately followed by in vitro fertilization. Thus, if clomiphene plus intrauterine insemination is unsuccessful, the next step is often in vitro fertilization.

Some evidence suggests that women who are over 38 and have unexplained infertility conceive more quickly when in vitro fertilization is done before controlled ovarian stimulation is tried.

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