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Unidentified Infertility Factors

By Robert W. Rebar, MD, Professor and Chair, Department of Obstetrics and Gynecology, Western Michigan University Homer Stryker M.D. School of Medicine

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 hyperstimulation

  • Sometimes assisted reproductive techniques

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

Controlled ovarian hyperstimulation may make pregnancy more likely and may help women become pregnant more quickly.

Controlled ovarian hyperstimulation 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 triggers ovulation, for up to three menstrual cycles. This treatment may result in more than one fetus.

  • Semen is placed directly in the uterus to bypass the mucus (intrauterine insemination) within 2 days after ovulation is triggered by treatment with fertility drugs.

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

Before assisted reproductive techniques are tried, some doctors give women human gonadotropins first, followed by hCG, and then intrauterine insemination is done within 2 days after hCG is given.

Sometimes the hormone progesteroneis given at a certain time during the menstrual cycle to increase the chances that a fertilized egg will attach to the lining of the uterus (see Figure: From Egg to Embryo).


Women have the same chance of pregnancy (about 65%) whether in vitro fertilization is done immediately after unsuccessful treatment with clomiphene plus hCG or whether human gonadotropins with intrauterine insemination are used next, before in vitro fertilization is tried. However, women become pregnant more quickly and are less likely to have a pregnancy with three or more fetuses when in vitro fertilization is done immediately after unsuccessful treatment with clomiphene plus hCG than when human gonadotropins are given before 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 hyperstimulation is tried.

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