How Intrauterine Insemination (IUI) Works
Intrauterine insemination (IUI) places sperm directly into the uterus to facilitate conception.
Intrauterine insemination (IUI), also known as artificial insemination, is a non-surgical procedure that places the sperm directly into the uterus. This is done by placing a long flexible catheter through the cervix, into the uterus and gently expelling the sperm. Before the IUI, the semen sample is collected by masturbation. Because of its alkaline pH, the seminal fluid can irritate the uterus, so it’s washed before insemination by spinning it in a centrifuge. Eggs are not retrieved for an IUI; fertilization and embryo development happen inside the body.
The IUI procedure is timed to coordinate with ovulation, so you may be asked to monitor your cycle with home ovulation predictor kits. When you see a positive surge in luteinizing hormone (the hormone that triggers ovulation), you call the clinic and make an appointment for your insemination the next day. Intercourse (and orgasm!) is encouraged following IUI to get the maximum amount of sperm to the egg. Check first with your doctor to make sure there was no bleeding during the IUI, which is very rare.
IUI is considered to be less invasive and less expensive than in vitro fertilization (IVF) and is a common first-line treatment for subfertility or infertility. Most physicians recommend advancing to the next form of treatment after six failed IUI cycles.
When is IUI used?
IUI can be used only if the fallopian tubes are open and you ovulate normally. Success rates of IUI vary considerably and are based on the number of follicles present, the sperm count, and any other underlying factors preventing you from getting pregnant.
- Unexplained Infertility - When no cause for infertility is found, IUI is a common first treatment option.
- Low Sperm Count - IUI has shown to be helpful in some cases of low sperm counts as the sample is centrifuged before insemination and the sperm are concentrated into a small volume of fluid. This allows more sperm to be introduced into the uterus than would happen following intercourse.
- Sperm Delivery Issues - IUI can be beneficial when there are ejaculation-related difficulties in delivering sperm into the vagina and in couples in which the male partner has decreased sperm motility.
- To Bypass the Cervix - IUI is also a good way to circumvent the cervix which may be beneficial in women who have had cervical procedures such as a LEEP or cold knife cone or other causes of cervical factor infertility.
- Third-Party Reproduction - When donor sperm is used to contribute to a pregnancy, it can be done with IUI and is called donor insemination.
Natural IUI Cycle
A natural cycle IUI (no medication) is usually recommended for women using donor sperm and who have no known fertility problems. The success rates for natural IUI cycles are approximately 15% in women using donor sperm with no known fertility problems.
The success rates for natural cycle IUI are approximately 3-5% in couples with unexplained infertility and are similar to the chance of pregnancy if they continued to try on their own or if they used oral medication and timed intercourse. Because of this, couples with unexplained infertility are recommended to consider medicated IUI cycles or IVF as needed.
Medicated IUI Cycle
A medicated IUI cycle follows the same basic principles as a natural cycle IUI. Both involve washing and concentrating the sperm and placing the sperm directly into the uterus. With a medicated IUI cycle, you take drugs to promote follicular development and ovulation.
Success Rates of a Medicated IUI Cycle
The success of medicated IUI is approximately 10-15% pregnancy rate per cycle, which is slightly higher than the natural cycle IUIs. The downside is the increased risk of a multiple pregnancy, especially when using injectable fertility drugs.
For that reason, it’s important to have regular ultrasound monitoring of the ovaries leading up to the insemination. If many follicles develop, you may be advised to cancel the cycle and use a lower dose of drugs next time. Alternatively, an IUI cycle can be converted into an IVF cycle if there is an unexpectedly high response. This is extremely uncommon with oral medications.
IUI with Clomid
One drug regularly used in medicated IUI cycles is Clomid, also known as clomiphene citrate. Clomid works on the brain and promotes the production of follicle-stimulating hormone (FSH). This hormone stimulates the growth of follicles in the ovary and is a first line of treatment to induce ovulation. The use of Clomid carries a 5% chance of twins and a rare chance of triplets. Because Clomid can change the cervical mucus and make it difficult for the sperm to swim into the uterus and fallopian tubes, it’s often recommended that Clomid be used in conjunction with intrauterine insemination, rather than intercourse, to maximize the chance of pregnancy. Clomid is relatively inexpensive, costing only a few dollars. However, a Clomid IUI cycle will likely incur additional expenses because of extra ultrasound monitoring and blood testing.
IUI with Letrozole
Letrozole (brand name, Femara) has similar effects as Clomid and similar success rates. It’s possible that patients who don’t respond well to Clomid or have intolerable side effects may do better using letrozole. One study in women with PCOS demonstrated a better chance of ovulation as well as pregnancy compared to Clomid.
If Clomid or Femara IUI is not successful, you may be advised to advance to the next level of treatment. This could be IUI with injectable fertility drugs, or it could be IVF.
IUI with Gonadotropins
Injectable gonadotropins are the same drugs used for IVF to produce many eggs at once. For an IUI cycle, the dose of gonadotropins is much lower than in an IVF cycle, with the intention of developing only two or three follicles before insemination. Because women respond differently to these injectable medications, the doctor follows the development of the follicles with ultrasound and possibly blood tests.
It’s important not to inseminate or have intercourse if you are at risk of a high-order multiple pregnancy (three or more mature follicles). Based on your age and diagnosis, the doctor assesses the risks of this happening, versus the chance of achieving a pregnancy, and proceeds accordingly.
Due to the much higher risk of twins and high-order multiples, most physicians recommend patients consider proceeding to IVF if they have failed prior IUI cycles with oral medications The cost of a gonadotropin IUI cycle can be around $2,500 per cycle.
FertilitySmarts uses high-quality sources to support the facts within our content including peer-reviewed studies, academic research institutions, professional organizations, and governmental organizations.
- Intrauterine insemination (IUI). (2019).
- Multiple Pregnancy and Birth: Twins, Triplets, and High Order Multiples (booklet). (2012).
- Clinical success of IUI cycles with donor sperm is not affected by total inseminated volume: a RCT. (2018).
- Letrozole versus Clomiphene for Infertility in the Polycystic Ovary Syndrome. (2014).
Written by Rebecca Matthews, PhD | Embryologist
Dr. Rebecca Matthews has a PhD in embryo implantation and currently works as an embryologist. Rebecca is passionate about her work and about educating and empowering people to take control of their own healthcare decisions. With this in mind, she has written an IVF guidebook to help patients understand the processes and options involved in fertility treatments. Her book, IVF: A Patient's Guide, can be found on Amazon.