A couple's ability to become pregnant depends on many different factors. Intrauterine insemination is used most often in couples who have:
- Donor sperm. For women who need to use donor sperm to get pregnant, IUI is most commonly used to achieve pregnancy. Frozen donor sperm specimens are obtained from certified labs and thawed before the IUI procedure.
- Unexplained infertility. IUI is often performed as a first treatment for unexplained infertility along with ovulation-inducing medications.
- Endometriosis-related infertility. Like unexplained infertility, the combination of medications to obtain the best egg and IUI is the first treatment.
- Mild male factor infertility (subfertility). Your partner's semen analysis, one of the first steps in the medical assessment of infertility, may show below-average sperm concentration, weak movement (motility) of sperm, or abnormalities in sperm size and shape (morphology). IUI can overcome some of these problems because preparing sperm for the procedure helps separate the highly motile, normal sperm from those of lower quality. This works best if the sperm have only one abnormality, such as only a motility problem.
- Cervical factor infertility. Your cervix is at the lower end of the uterus and provides the opening between your vagina and uterus. The mucus produced by the cervix around the time of ovulation is supposed to provide an ideal environment for sperm to travel from your vagina to the fallopian tubes. However, if the cervical mucus is too thick, it may impede the sperm's journey. IUI bypasses the cervix, depositing sperm directly into your uterus and increasing the number of sperm available to meet the awaiting egg.
- Semen allergy. Rarely, women have an allergy to proteins in their partner's semen, so ejaculation into the vagina causes redness, burning and swelling where the semen has contacted the skin. A condom can protect you from the symptoms, but it also prevents pregnancy. If your sensitivity is severe, IUI can be effective, since many of the semen proteins are removed before the sperm is inserted.