What is Intrauterine Insemination?

Intrauterine Insemination

The most common type of artificial insemination is intrauterine insemination (IUI), which is the process of selecting the most normally-shaped, best swimming sperm from a semen sample, washing off the seminal plasma, and using a sterile catheter deliver the sperm as close to the ovary as possible during ovulation. Frequently, an ultrasound is used to see which side the patient is ovulating from, and whether ovulation has already occurred. Seminal plasma is the fluid the sperm are naturally delivered in, and it must be washed off because it is highly antigenic and could cause a severe allergic reaction if it were forcibly injected into the uterus. While preparing the sperm the sample is often treated with nutrients, such as fructose and amino acids. Additives, such as caffeine, can be added to improve motility.

The fundamental goal of IUI is to increase the number of functional sperm reaching the ovaries during ovulation, which can greatly increase the chances of conception. Intrauterine Insemination (IUI), is to be distinguished from Intracervical Insemination (ICI), a procedure in which when the sperm are placed shallowly into the cervix. Clinical studies have demonstrated the superiority of placing the specimen high into the uterus, which generally requires performing an ultrasound before the procedure to know which way to go. These two procedures are also sometimes called “artificial insemination.” 

When is Intrauterine Insemination done?

Intrauterine insemination is performed the day after a positive color change with the ovulation predictor kit, or following an injection of human Chorionic Gonadotropin (hCG), which is given to cause or strengthen ovulation. An ultrasound can detect if the follicle has already released the egg, which is desirable because the egg has to be out of the ovary in order to fertilize. A sterile speculum is used to access the cervix. The cervix is cleansed with cotton swabs, and a soft plastic catheter is placed high in the uterus - as close to the tubal opening as possible. Using gentle pressure, the contents of the catheter are directed toward the tubal opening, flushing the sperm through the tube into the pelvis. The goal is to saturate the fluid around the ovary with millions of fortified sperm, within hours of ovulation.

What sort of Problems does IUI Treat?

This technique essentially gives the man’s sperm a “head start” by avoiding any naturally occurring barriers or obstructions. By selecting the most normally shaped sperm, and best swimmers, IUI can help correct for problems with low sperm count, diminished seminal volume, or a high percentage of abnormally shaped sperm. Special sperm preparations can improve problems with sperm motility.  IUI is useful in overcoming “hostile” cervical mucus. 

Sometimes intercourse is uncomfortable, or physical or anatomical factors such as cervical stenosis, either congenital or as the result of treatment for an abnormal pap smear has resulted in narrowing or scarring of the cervix. A certain number of women are born with smaller than usual cervical openings called “pin-hole” cervix. It is estimated that 5 to 10 million sperm must be delivered to the top of the uterus for a couple to meet their age-relation probability of conception, however pregnancies have occurred with as few as a quarter million sperm if the insemination is timed properly. So, couples with even severe male factor infertility are encouraged to try IUI at least a few times.  


It is important to note that insemination does not treat, or get around, endometriosis. Endometriosis is a condition caused by endometrial tissue, the tissue that normally lines the inside of the uterus, growing outside of the uterus, in the pelvis. Bits of the tissue float through the fallopian tubes during your period and take up residence in the pelvis. Normally white blood cells (WBC) come to the area and produce chemicals that dissolve the implants, typically within days of when your period ends. Some women have WBCs that lack all the chemicals needed, and the develop “endometriosis.”

The problem is the tissue continues to cycle, responding to the hormones as it did before it was misplaced. When you have your period, these implants bleed, causing inflammation and scarring. It is why women with endometriosis have very painful periods. The other issue is that because the WBCs never finish the job, they never leave the area. They remain in the pelvic fluid producing harsh chemicals that damage the egg and the sperm, and prevent fertilization. Endometriosis can be treated most directly by destroying the implants surgically, or by denying the tissue estrogen, the hormone needed for it to grow.

Hostile Cervical Mucus

At puberty, a girl’s uterus grows from a structure not much bigger than a ping-pong ball to become the size of her adult fist. During that time the cavity opens up, and could act as a pathway for harmful bacteria to enter her body. So, during puberty, girls begin to allow certain bacteria, called Lactobacillus, to colonize the vagina. This turns the pH acidic which protects them from various pathogens that might otherwise cause harm. The peak in estrogen at mid-cycle that causes the LH surge, also stimulates cells that line the cervix to make cervical mucus.  

Under the best circumstances, the cervical mucus acts as a pH buffer protecting the sperm from the acidic environment that is normally present in the vagina and helps transport the sperm up into the uterus. Until a couple has had a successful pregnancy together, the woman’s immune system sees his sperm as “invading” her body. This can cause something like an allergic reaction in the cervical mucus, immobilizing or killing a majority of the sperm. Intrauterine insemination is a way around “hostile” cervical mucus.

Fortunately, once the woman has successfully carried a baby whose genetic code is half from the father, her immune system is altered, and further exposure to his sperm isn’t likely to cause as much of an alarm.

“Back-to-back” Insemination

If the egg has not yet been released at the time of a first insemination, patient might be instructed to come back a second day. This practice, doing “back-to-back” inseminations, is done if the day after a positive Ovulation Predictor Kit (OPK), ovulation has not fully occurred. The positive OPK means the LH surge has begun, but it takes 36 hours for the egg to go through a “reduction division” pair down half of the egg’s chromosomes and be ready to accept the new set of chromosomes carried in the sperm. Additionally, depending upon which medications the patient may be taking to enhance ovulation there may be more than one mature follicle, and ovulation could easily be a 2-day event. Performing two inseminations back-to-back, increases the odds that an egg and sperm will be in the right place at the right time.

Is Intrauterine Insemination Painful?

For the patient the sensation should be like having a Pap smear. Afterwards, it takes approximately 20 minutes for the sperm to travel through the fallopian tube(s) into the pelvis, so the clinicians generally have you remain on the exam table for a period of time after the procedure. (It is a good time to check email.)  After that, you can resume normal activity.  

Typical Work-up

There are a number of steps involved in your evaluation prior to recommending procedures such as intrauterine insemination. A careful work-up would involve: (1) a cycle evaluation demonstrating that you are ovulating well enough to become pregnant, often with ovulation enhancing drugs; (2) a semen analysis to determine how many sperm your husband produces and how well they function; and (3) documenting normal pelvic anatomy either by an x-ray, called a Hysterosalpingogram (HSG), or by a Saline Infusion Sonogram (SIS). Many clinicians want to prove that you are ovulating well enough to become pregnant before committing you to your first insemination, to avoid causing a situation where you might otherwise miscarry.  

When to do Intrauterine Insemination?

There is no one definitive criteria for evaluating the need for fertility treatment as each couples’ situation is unique. However generally speaking, hopeful parents who are 35 years old or younger should try to conceive naturally, via sexual intercourse for 6 months before considering a need for intervention. Some cell phone “apps” are helpful. There are also sensitive ovulation predictor kits, Clear Blue Easy, which measures partial and intact molecules of LH, giving a blinking “smiley face” during the rise of the hormone, turning solid at the peak, is regarded as the most accurate by infertility specialists. Should conception not occur after six months, a fertility consultation is advisable. If you have a known medical condition that could impair the reproductive process, or a strong family history of difficulty conceiving, you might start with a consultation to evaluate if you too are at risk.

How long is it Appropriate to do Insemination?

One of the definitions of infertility is “the inability to achieve a pregnancy within twelve months of unprotected intercourse.”

Once you have begun treatment, once you have documented the woman’s fallopian tubes are open, and you are timing exposure correctly, unless you are dealing with extremely few normal, motile sperm, a pregnancy should occur within four cycles. Situations where that has not occurred require further evaluation. If you were trying insemination with very low sperm counts just to see if IUI could work, it is time to move on to in vitro fertilization. It is possible that endometriosis is preventing fertilization. You might proceed to an outpatient surgery, called laparoscopy, to diagnose and treat endometriosis.