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In vitro fertilization (IVF) often gets most of the attention when people talk about fertility treatment, leaving its simpler, cheaper, and less invasive alternative in the shadows: intrauterine insemination (IUI). While IVF can be a very effective treatment option, it isn’t necessarily the best first choice for everyone — for some, IUI might be the right move.
With IUI, the sperm is directly put into the uterus just before ovulation (when an egg is released from an ovary), increasing the likelihood that sperm and egg will meet. With IVF, on the other hand, a previously retrieved egg (the same process that kicks off egg freezing) is fertilized in a lab and transferred into the uterus. Because fewer procedures and medications are required, IUI is often significantly less expensive than IVF: IUI can run you a few hundred to $1,000 per cycle versus around $11,000-$15,000 per cycle for IVF without medication. Although IUI may be less successful than IVF, the cumulative success rate of several cycles of IUI can approach the same success rates seen in a cycle of IVF.
In this post, we’ll get into the nitty-gritty of what IUI is, what you can expect the procedure to be like, what options you’ll have to choose from, what factors predict success rates, and questions you can ask yourself to decide if IUI is right for you.
- IUI is a procedure where sperm is directly put into the uterus just before ovulation (when an egg is released from an ovary).
- The main goal of IUI is to get the best quality sperm closer to the egg prior to ovulation. Commonly cited success rates range from 10% to 20% cycle.
- IUI is typically only used for up to three or four cycles — chances of success drop off after that. At that point, other treatments (like IVF) will usually be explored.
- Some of the factors that influence IUI success rates include age, sperm count and morphology (shape), and fallopian tube patency (i.e., no obstructions).
- Talking to a reproductive endocrinologist about your health history (plus your partner’s if applicable) and fertility work-up results is a great way to figure out whether IUI is a good option for you.
What is IUI and how does it work?
When compared to IVF — which may involve several different medications and doctor visits — a basic IUI procedure can be done relatively simply. According to Dr. Julie Lamb, MD, FACOG, a reproductive endocrinologist at Pacific Northwest Fertility and a member of the Modern Fertility Medical Advisory Board, the main goal of IUI is to “get the best quality [sperm] closer to the egg and waiting for the egg prior to ovulation.”
Dr. Lamb explains that IUI treatment plans will typically be different for people conceiving with a partner who also has ovaries, people conceiving on their own, and people who don’t have ovulatory (aka with ovulation) cycles. Still, age, ovarian reserve (egg count), and family-building goals will weigh heavily into the decisions made around any individual’s treatment plan.
At its *most* basic, IUI can involve zero medications and a single visit to the doctor’s office (your OB-GYN might even do them!):
- A doctor will ask you to monitor ovulation at home using ovulation predictor kits (OPKs). Once you detect a surge in luteinizing hormone (LH), the hormone that coaxes an egg out of an ovary during ovulation, you’ll come into the office.
- If you’ve got a partner with sperm, they’ll provide a semen sample on the spot. If you’re using a donor and/or frozen sample, that sample will be thawed.
- The sample will be “washed,” meaning mostly everything other than the sperm itself will be removed. What’s left will be a very concentrated collection of sperm.
- Using a super thin catheter, a medical professional will go through your cervix and insert the sperm into your uterus. Studies suggest that doctors and nurses have similar success rates here, meaning it doesn’t matter who performs the procedure (assuming they’ve had the clinic-required training).
- Sometimes you’ll be instructed to lie down for a bit after the insertion. While there isn’t much data to suggest this helps your chances of conception, it certainly doesn’t harm them.
In this “basic” scenario (which is also sometimes referred to as “natural cycle IUI”), there are very few complications or side effects from the procedure. Some people do report some light cramping after the insertion, but that typically fades that same day or the next.
Just as there are add-ons in the IVF world, there are add-ons in the IUI world as well:
- Pre-procedure medications: Doctors may choose to prescribe pre-procedure medications that encourage ovulation. In cases where someone is producing ovarian hormones (like LH and follicle-stimulating hormone, or FSH) but isn’t ovulating, they’ll likely be prescribed ovulation-induction meds like clomiphene citrate (aka Clomid) or letrozole (aka Femara). These meds may also be prescribed in cases of unexplained infertility (where there are no detected abnormalities in ovulation) and seem to boost pregnancy rates (see here, here, and here).
- Gonadotropins: Gonadotropins, which is a fancy word for injections of hormones like FSH, can induce follicular growth and ovulation for those who aren’t ovulating but want to try IUI.
- Ovulation trigger shot: It’s possible to monitor spontaneous (aka untriggered) ovulation via LH ovulation predictor kits at home, or your doctor may prefer to use an ovulation trigger shot (this could be human chorionic gonadotropin, aka hCG, or Lupron) to more precisely control the timing of ovulation.
- Multiple insemination cycles: While some clinics opt for one insemination session per cycle, others may go for two. The literature is pretty mixed on whether or not double insemination offers any advantages, but a potential disadvantage is the cost of additional cycles.
- Progesterone supplementation: A fertilized egg needs to dig its heels into a well-developed endometrium (aka uterine lining) for a pregnancy to be established, and endometrial development is in large part driven by the hormone progesterone. Some doctors will prescribe progesterone supplementation after IUI to increase the chances of implantation and keep the uterine lining from shedding.
IUI is sometimes used as a first-line treatment: something that’s recommended before opting for more involved and costly IVF procedures. There are even some insurance companies and plans that will not cover IVF procedures unless someone tries IUI first. But there are limits to how many times IUI cycles should be attempted. Clinics will often try IUI for up to three or four cycles because, after that, success rates drop off. At that point, other options (like IVF) should be considered.
How successful is IUI? And what factors can influence success rates?
While some people will often report a general 10%-20% success rate for IUI, the numbers for specific subgroups and scenarios can be considerably higher or lower — though there’s surprisingly little consensus about what the exact numbers for these specific subgroups are. Knowing where you may stand on these factors can help you get more specific and personalized ideas of what your success rate could look like.
Just as age impacts things like number of eggs, the quality of those eggs, and chances of conception during unassisted conception, the age of the person undergoing IUI can impact their chances of success.
Data from one recent study of over 92,000 cycles and 38,000 patients demonstrated a clear link between age and IUI success rates. Here were their per-cycle pregnancy rates across age groups:
- 19% for people under 35
- 15% for people between 35 and 37
- 13.4% for people between 38 and 40
- 12% for people over 40
This means relative to people under 35, people over 40 have success rates that are almost cut in half.
We can also look at cumulative success rates — i.e., how many people eventually ended up getting pregnant after several IUI cycles — and still see the same age effect at play. Data from over 4,100 cycles at one center reported the following cumulative success rates:
- 24% for people under 35
- 19% for people between 35 and 37
- 15% for people between 38 and 40
- 7% for people 41 or 42
- 2% for people over 42
This age effect has been reported in several different studies (here, here, here, and here), and is also seen in IVF success rates and conception rates without medical assistance, so we can be confident it’s a real (albeit frustrating) phenomenon we’re observing. The age effect here is so reliable and so considerable that for certain age bins, it’s recommended that people skip IUI altogether and try IVF instead. Some data indicates that the per-cycle chance of success for IUI is below 1% for people 44 and older.
IUI is often used as a way to help when there are issues with sperm, like a low total motile sperm count (the number of sperm that are able to move), a high percent of sperm with abnormal morphology (sperm with abnormal shapes), or a high percentage of sperm with DNA damage. During unassisted conception, some sperm is naturally filtered out by the cervix and doesn’t make it to the uterus. By surpassing the cervix, IUI can help maximize the number of sperm that could reach an egg during ovulation — which may be particularly helpful in cases with low sperm count.
The relationship between sperm count and IUI success rates isn’t exactly a linear one, but generally speaking, a higher sperm count is associated with a higher likelihood of success. There are floor effects, which means that any sperm counts below approximately 1 million all have similar success rates (i.e., the lowest success rates of all groups). There are also ceiling effects, which means that any sperm counts above approximately 9 million have similar success rates (i.e., the highest success rates of all groups). For everything in the middle, slight increases in sperm count are associated with slight increases in success rates.
That same study of over 92,000 cycles we just talked about in the previous section? In addition to looking at the effect of age on IUI outcomes, they looked at the effect of total motile sperm count (TMSC). The clinical pregnancy rates per-cycle were the following for different sperm count bins:
- 4% for TMSC below 1 million
- 7.5% for TMSC from 1 million to right under 2 million
- 10% for TMSC from 2 million to right under 3 million
- 12% for 4 to right under 5 million
- 13% for 5 million to right under 6 million
- 14% for 6 to right under 7 million
- 14% for 7 to right under 9 million
- 17% for over 9 million
IUI can be done with either fresh or frozen-thawed sperm. While some studies have found a slight advantage of fresh over frozen, others have found success rates for frozen-thawed sperm that are similar to what we’d expect when using fresh sperm. One thing to keep in mind is that not all frozen sperm survive the thawing process (a 2019 study cited a survival rate of around 85% if sperm is frozen for under five years).
IUI may also be particularly helpful in cases where issues with erection or ejaculation are at play. By putting the sperm exactly where they need to be, any complications associated with these issues are removed from the equation.
The cervix plays no small role in the conception process: It serves as a formidable barrier that sperm need to pass to get to the uterus and eventually the egg. In cases where cervical factors may be causing infertility (i.e., in cases of “hostile” cervical mucus that’s less conducive for sperm to travel through — which is a phrase we’re all for retiring), IUI may be especially helpful relative to other interventions like timed intercourse or intracervical insemination (ICI). That being said, cervical factors are identified as the cause of infertility for a vanishingly small percentage of people.
Fallopian tube anatomy
One potential cause of infertility for people with ovaries is fallopian tube blockage. Sperm and eggs typically meet in the fallopian tube before migrating down to the uterus, and blockage of the fallopian tubes gets in the way of this meet-up. One or both fallopian tubes can be blocked, and this is often investigated through a procedure called a hysterosalpingogram (HSG): an X-ray of your uterus and fallopian tubes.
In cases where both tubes are blocked, IUI won’t be recommended. Even though IUI will get the sperm to the uterus, fallopian tube blockage will prevent them from getting to the egg — meaning conception won’t be possible. Because of this, it’s best to first rule tubal blockage out before assuming IUI may be helpful for you.
If you’re considering IUI because you’ve been trying to get pregnant without success for 6-12 months, depending on your age, your doctor might do an HSG as part of your infertility work-up (which can also include blood tests and ultrasounds).
People who have milder stages of endometriosis are good candidates for IUI if they have unobstructed fallopian tubes and an egg count that’s considered “normal” for their age — but those with more advanced stages of endometriosis and blocked tubes are not. People in this latter category are typically recommended to pursue other treatment options, such as IVF.
Number of follicles
Most people during most (but not all!) cycles will release one egg during ovulation. In cases where ovulation-induction medications like Clomid or Letrozole are being used, or when more potent and strong fertility medications are being used, your doctor will likely be monitoring you to see how many follicles (the fluid-filled sacs that house and develop eggs) are developing because the chances of ovulating multiple eggs will be higher.
Some meta-analyses have found that the number of developing follicles is associated with a higher chance of success in IUI — while the chance of pregnancy was 8.4% for cycles where one follicle developed, it was roughly 15% for cycles where there was more than one developing follicle. That being said, there are some risks associated with shooting for more than one follicle. Most notably, multiple follicles means a higher chance of carrying multiples, which can have risks of its own (like preterm birth, gestational diabetes, and preeclampsia).
How do success rates for IUI stack up to alternatives?
Researchers have compared IUI to a couple of other treatment strategies over the years. While how IUI stacks up largely depends on the subgroup we’re looking at, we can zoom in on the performance of IUI as compared to other treatments in cases of unexplained infertility (when there’s no clear diagnosis for infertility).
IUI versus IVF
In some cases, a couple of rounds of IVF can yield success rates that are similar to that of IVF:
- One study of over 200 couples randomized to get either one IVF cycle or three cycles of IUI + gonadotropins found that overall pregnancy rates were comparable for both groups at the end of the study. (While rates were higher in the IUI group, the difference wasn’t statistically significant.)
- An analysis of almost 320,000 cycles in the UK found that while live birth rates were different per cycle for IUI and IVF, IUI was much more cost-effective — meaning that when you took the different success rates into account, the amount of money spent to achieve a live birth was significantly lower for IUI than it was for IVF.
IUI versus ICI
Intracervical insemination (ICI) differs from IUI in one major way: Whereas in IUI the sperm gets a VIP pass past the cervix and gets inserted right into the uterus, sperm gets injected at the cervix in ICI. This means in ICI, there are additional barriers sperm need to pass that don’t exist in IUI. Some studies (like this one) find that success rates are comparable in IUI and ICI, while others (like this one) suggest a benefit to IUI over ICI.
IUI versus timed intercourse
Knowing when your fertile window is and timing sex around that is one of the most powerful things opposite-sex couples can do if they’re trying to conceive because conception is only possible during a specific window within the cycle. The jury is out on whether IUI is associated with significantly higher success rates than timed intercourse alone for opposite-sex couples with unexplained infertility, probably in part because there have not been all that many studies designed to answer this question.
All of that said, the chances of conception differ significantly based on how long someone has been trying to conceive. If someone has been trying to conceive for more than six months without getting pregnant, their per-cycle chances of conceiving without medical assistance are lower than they would be with IUI.
How do you know if IUI is a good option for you?
The more info you have, the better armed you can be to make a well-informed, confident decision about what fertility treatment options, if any, make sense for you. Here are some things to talk about with a reproductive endocrinologist (aka a fertility specialist) if you’re weighing the pros and cons of different types of fertility treatment:
- If you’ve been trying to conceive with a partner who produces sperm and you haven’t had any success yet, is there an identified cause? This is a big one in helping either eliminate possible options or making others more promising. For example, IUI probably isn’t the best option for cases where sperm count is abnormally low (making procedures like IVF a better bet).
- What do success rates look like across different treatment options at the same clinic? While the Society for Assisted Reproductive Technology (SART) publishes yearly reports on success rates for IVF, a comparable resource doesn’t exist for IUI success rates. Similarly, the clinic reports published by the Centers for Disease Control and Prevention (CDC) don’t publish success rates for IUI. If success rates for IUI and IVF seem close but IUI is substantially cheaper, it may warrant trying a few cycles of IUI before moving to costlier procedures. Which brings us to our next point…
- If you have insurance, what will it cover for different treatments? Some insurance companies won’t cover IVF unless a few cycles of IUI have been attempted first, which may be something worth keeping in mind when figuring where to start with treatments. It’s also important to note here that it might be challenging to get fertility treatment coverage if you haven’t been trying to conceive for at least 6-12 months — the definition insurance providers often use for infertility. Many plans, unfortunately, aren’t designed for all paths to parenthood (like conceiving on your own or with a partner who has ovaries). If you have insurance through an employer, it could be helpful to reach out to HR about fertility benefits or LGBTQ+-friendly insurance plans.
The bottom line on IUI
Just like there’s no absolute predictor of fertility, there aren’t any fertility treatments that guarantee a pregnancy — and IUI is no exception. There are several factors that make success with IUI (and with other treatments like IVF) more or less likely, and understanding how these factors relate to you may help give you an idea of whether IUI is a good option.
Thinking that another fertility treatment might make more sense for you? The Modern Fertility blog has you covered with IVF success rates, a step-by-step guide to egg freezing, and an overview of assisted reproductive technology in general.
This article was reviewed by Dr. Julie Lamb, MD, FACOG, a reproductive endocrinologist at Pacific Northwest Fertility and Modern Fertility medical advisor.