How does IUI work?

What is intrauterine insemination (IUI)?

IUI is a procedure that places sperm past the cervix and into the uterus around the time of ovulation. The goal is to shorten the sperm’s trip to the fallopian tubes, where fertilization can happen if an egg has been released ASRM.

In a natural pregnancy, sperm travel from the vagina through the cervix, into the uterus, and up to a fallopian tube. The cervix acts as a natural filter, so only a small percentage of sperm in one ejaculation reach the tubes. IUI works by helping more sperm get closer to the egg ASRM.

When might IUI be helpful?

IUI can be useful for several infertility situations. The most common use is unexplained infertility, when no clear cause is found. It may also help when the cervix has scarring or an unusual shape that makes it hard for sperm to pass, when sperm delivery is a problem, when ovulation is irregular, or when donor sperm is being used ASRM.

For some patients with unexplained infertility, IUI is paired with medicines that help the ovaries mature more than one egg. The idea is to increase the chance that sperm will meet an egg. IUI can also be used with frozen sperm collected before cancer treatment, vasectomy, or testicular surgery ASRM.

How is the sperm collected?

Most often, the male partner collects a sample by masturbation into a sterile cup provided by the office or laboratory. Another option is collection during sex in a special condom provided by the doctor. If sperm are being affected by retrograde ejaculation, the sperm can sometimes be retrieved from urine in the lab ASRM.

When ejaculation is difficult, sperm may be collected with vibratory stimulation or electroejaculation. These methods are also used for some patients with spinal cord injury. In the case of complete spinal cord injury, electroejaculation is commonly done in the office; with an incomplete injury, it may be done under anesthesia in the operating room ASRM.

What happens in the lab before IUI?

Before insemination, the semen sample is “washed” in the laboratory. This concentrates the sperm and removes seminal fluid, which can cause severe cramping in the female partner. The washing process can take up to 2 hours ASRM.

That preparation matters because IUI uses a smaller, cleaner sample than a standard ejaculation. The lab step does not change the basic purpose of the procedure: to place sperm directly in the uterus near the time an egg may be available ASRM.

What does the IUI procedure involve?

IUI itself is usually quick and relatively simple. The patient lies on an exam table, a speculum is inserted to see the cervix, and a thin catheter is passed through the cervix into the uterus. The washed semen sample is then slowly placed into the uterus ASRM.

The procedure is done near ovulation, when an egg may be present in the fallopian tube. Once the sperm are inside the uterus, they have a shorter distance to travel, which may improve the chance that sperm and egg will meet ASRM.

What does IUI feel like?

IUI is usually painless, though some people have mild cramping. Spotting for a day or two after the procedure can also happen ASRM.

Because the sperm are placed into the uterus after being washed, seminal fluid is removed first. That step helps reduce the chance of cramping during the procedure ASRM.

How well does IUI work?

IUI works best for unexplained infertility, for cervical problems that block sperm passage, and for male-factor problems where ejaculation is ineffective. It can also help in some cases of ovulation problems when it is combined with ovulation-inducing medication ASRM.

It does not work as well when sperm counts are very low or sperm abnormalities are severe. It also does not help when there is severe fallopian tube disease, moderate to severe endometriosis, or a history of pelvic infections. In those cases, other fertility treatments are usually better options ASRM.

Success also depends on factors such as whether fertility medicines are used, the age of the female partner, and the infertility diagnosis. ASRM notes that for unexplained infertility, pregnancy rates with IUI plus ovulation medication are double those with no treatment ASRM.

What are the risks of IUI?

The main added risk comes from fertility medicines, not from IUI itself. If medicines are used to mature more than one egg, the chance of twins, triplets, or more is higher than without those medicines ASRM.

IUI does not increase the risk of birth defects. The overall chance of birth defects in all children is 2% to 4%, whether conception happens naturally or with IUI. Infection after IUI is possible, but the risk is small ASRM.

How does IUI fit into fertility care?

Infertility can happen for many reasons, including problems with ovulation, blocked or damaged fallopian tubes, uterine conditions such as fibroids or endometriosis, or sperm issues such as low count or poor movement. It is defined as not becoming pregnant after frequent, unprotected sex for one year, or after six months if someone is age 35 or older MedlinePlus.

That broad range of causes is one reason IUI is used selectively rather than as a universal treatment. A careful diagnosis helps match the procedure to the type of infertility involved, because treatment depends on the cause, how long someone has been trying, and age MedlinePlus.