Why It Might Not Work
Many health professionals say that intrauterine insemination in a highly effective form of assisted reproductive technology. It involves introducing washed sperm directly into the uterus with a syringe and a tube through the cervix. The procedure can have a success rate as high as 20 percent but it only works as a treatment for some causes of infertility. It's commonly used in cases of unexplained infertility, mild endometriosis, ovulation problems, cervical factor infertility and mild male factor infertility. But it doesn't work with ovarian failure (regular or early menopause), severe male factor infertility, advanced endometriosis, or severer tubal damage or tubal blockage. The procedure usually isn't performed on women over the age of 41.
Ovarian Failure
As women get older, their egg quality and quantity declines which is why there's a female age cut-off for IUI. Generally a 43-year-old will be less fertile than a 30-year-old; however there are exceptions to the rule. In some cases, women can already experience a fertility decline as early as their teens and twenties.
There aren't very many reliable tests to determine a woman's quality and quantity of eggs, but there are a few screening tests that can provide some insight. These tests are referred to as ovarian reserve testing because they try to determine the supply (reserve) of eggs still available in the ovaries. It rarely can tell the specific quantity of eggs available, but in can give an idea of the quality of those eggs. Ovarian reserve testing usually involves monitoring of the follicle stimulating hormone.
Age in men is rarely a factor is the quality of sperm produced. Sperm are constantly being produced so they're always new, while a woman is born with a certain amount of eggs at birth and does not produce any more. These eggs can also age which can lead to infertility.
Tubal Damage or Tubal Blockage
Any type of fallopian tube damage will reduce the effectiveness of IUI. In order for IUI to work, there needs to be access to healthy eggs for the injected sperm to fertilize. Fertilization occurs in the fallopian tubes and this can't happen if the tubes are blocked. Blocked tubes can be diagnosed with a hysterosalpingogram, a procedure done in the radiology department involving the injection of a special dye into the uterine cavity and an x-ray.
Advanced Endometriosis
Endometriosis is a condition where the endometrial lining of the uterus grows outside the uterus or attaches itself to other internal organs. The lining can't be shed like the lining inside the uterus is during menstruation. It eventually forms scar tissue or lesions. Endometriosis can often be treated if it's mild or caught early enough, but advanced endometriosis often causes extensive scarring and damage to the uterus and ovaries that make ovulation and embryo implantation impossible.
Severe Male Infertility
In severe cases of male infertility there are so few or no viable sperm produced that there's nothing to work with for the IUI procedure. If the male partner can't produce enough or any healthy sperm, donor sperm may be used.