Why it's done

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. For infertility related to endometriosis, using medications to obtain a good-quality egg along with performing IUI is often the first treatment approach.
• 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 highly motile, normal sperm from those of lower quality.
• Cervical factor infertility. Your cervix, at the lower end of the uterus, provides the opening between your vagina and uterus. Mucus produced by the cervix around the time of ovulation provides an ideal environment for sperm to travel from your vagina to the fallopian tubes. But, if your cervical mucus is too thick, it may impede the sperm's journey. The cervix itself may also prevent sperm from reaching the egg. Scarring, such as that caused by a biopsy or other procedures, can cause the cervix to thicken. IUI bypasses your cervix, depositing sperm directly into your uterus and increasing the number of sperm available to meet the awaiting egg.
• Ovulatory factor infertility. IUI may also be performed for women who have infertility caused by problems with ovulation, including an absence of ovulation or a reduced number of eggs.
• Semen allergy. Rarely, an allergy to proteins in semen can cause infertility. Ejaculation into the vagina causes redness, burning and swelling where the semen contacts 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 proteins in semen are removed before the sperm is inserted.