How many sperm do you need for intrauterine insemination (IUI)?

Intrauterine insemination (IUI) is a popular first line fertility treatment option for couples who struggle to conceive on their own. It is particularly effective for couples who have difficulty with ovulation, cervical issues, low sperm count, sexual dysfunction, unexplained infertility or mild endometriosis.

What is an Intrauterine Insemination?

Intrauterine insemination (IUI), is a fertility treatment where a doctor places sperm inside a woman’s uterus to help improve chances of conception. By inserting the sperm directly into the uterus, you reduce the distance sperm need to swim to reach the egg. This enables more sperm to swim into the fallopian tubes and increases your chances of getting pregnant.

Incredibly, the first IUI’s were done centuries ago in the 1770s. As you’d expect these early attempts were relatively simple procedures. Semen was collected and literally loaded into a turkey baster to be injected into the woman’s vagina. Since then, the procedure has become appreciably more sophisticated. These days, the woman’s ovulation cycle is monitored to ensure ideal timing for the procedure. In many cases the woman will use Clomid or gonadotrophins (fertility injections) to stimulate mature eggs in the ovaries, to mature eggs followed by a trigger shot (hCG) to induce ovulation. Prior to insemination, the man’s semen goes through special preparations (called “washes”) to remove dead sperm and optimize the fluid around the sperm to give them an extra boost. Finally, specially designed catheters enable doctors to place sperm in the best possible location within the uterus. Some doctors will use an ultrasound to help guide the catheter.

What is the success rate for an IUI cycle?

The European IVF Monitoring Consortium collects data on every assisted reproduction procedure done in Europe. A recent report analyzed data gathered from 1.5 million IUI cycles from 1997 – 2011 and shows that 11.8% of those IUIs resulted in a pregnancy. Thus it often takes more than one IUI cycle to achieve a pregnancy.

As with natural conception, chances of pregnancy are higher for younger women and men with higher quality semen. Rates are highest among single or lesbian women who don’t have fertility issues and use donor sperm (aka very high quality sperm). In these cases, chances of pregnancy are around 20% in each cycle.

When should you get an IUI?

Generally, doctors do not recommend fertility treatments unless a couple has been trying unsuccessfully to conceive for at least 12 months, or for 6 months if they are over age 35. There are a few exceptions to this for single women, transgender or lesbian women for whom natural conception isn’t possible.

As a rule of thumb, doctors like to start with least invasive, lowest risk interventions. In the case of conception, the lowest risk things to do to increase chances of getting pregnant include lifestyle changes to improve health and fertility, tracking ovulation cycle with predictor kits or basal body temperature monitoring, and having regular intercourse. If those things are not sufficient, the next step is to evaluate both partners to identify issues that contribute to difficulty conceiving.

A standard evaluation for a woman includes a medical history, physical exam and blood tests. Doctors look for signs of endometriosis, lack of ovulation, blockages, scarring or other issues that could contribute to difficulty conceiving. For men, a semen analysis is a general first step. An abnormal semen analysis should trigger a full evaluation which should also include medical history, physical evaluation and blood tests.

Intrauterine insemination is often recommended if:

  • The man’s semen analysis comes back low but not too low
  • There are issues with the cervix (such asor has hostile cervical mucus)
  • A woman has trouble ovulating
  • A woman has mild endometriosis

IUIs are not recommended for women who have blocked fallopian tubes, previous pelvic infections or moderate to severe endometriosis. There is a lot of debate in the medical community around when to recommend IUI versus other forms of fertility treatment particularly in cases of unexplained infertility.

Can an IUI help you get pregnant if you have a low sperm count?

The short answer is yes.

The more, healthy sperm a man has, the better the chances of conception. As sperm count goes down, so do chances of conceiving each month. When sperm count drops below 10M/mL, the odds of natural conception drop down to 5 – 10% or lower each month. With IUI, doctors can take the limited number of sperm available and place them closer to the egg to therefore increase the chances that one of them will successfully fertilize. Overall this can double or triple your chances on conceiving during a given month compared to timed, natural intercourse.

What’s the minimum number of sperm required for an IUI?

While doctors and researchers have a hard time agreeing on what a good minimal number of sperm are required for an IUI, they all agree that “more is better”. As the number of healthy sperm goes down, so do the chances of conception – even with an IUI. Many clinics recommend in vitro fertilization (IVF) over IUI in cases of low sperm count because the odds of pregnancy are typically much higher for an IVF cycle compared to an IUI cycle. However, IVF is also more expensive and invasive which makes the decision much less clear cut.

There are two main ways to think about the number of sperm needed for an IUI. First, you can consider the total number of swimming sperm that are ejaculated from the body and end up in the cup. This is called the total motile sperm count (TMSC) and is calculated by multiplying the sperm concentration (M/mL) by % motile by the total volume.

Sperm Concentration (M/mL) X Sperm Motility (%) X Semen Volume (mL) = Total Motile Sperm Count (M)

Total motile sperm count can range from 0 to more than 200 million sperm. Some doctors like to see a minimum of at least 1 million motile sperm, while others prefer the number to be higher – 3 million, 5 million or 10 million have all been recommended as cut-offs for an IUI cycle. Again, the higher the number, the better the chances.

Another way to think about sperm needed for an IUI is the number of sperm that are injected into a woman. This is a more common way to measure sperm counts when handling frozen samples. Clinics usually refer to this as the post-wash total motile count. The lowest cut-off reported in literature is 800,000 million motile sperm, although most clinics like to see between 1-5 million motile sperm post-wash used for insemination.

What is the difference between a pre-wash and post-wash sperm count?

As mentioned above, sperm samples collected for an IUI are treated or “washed” to improve outcomes. Semen preparation techniques separate healthy, motile sperm from semen and leave behind dead or immature sperm, white blood cells, bacteria and oxygen radicals that can negatively impact a sperm’s ability to fertilize an egg.

When preparing a semen sample for use in an intrauterine insemination, the technician will do a quick semen analysis of the raw sample. A tiny drop is taken from the sample and placed on a slide. The technician will count the number of sperm cells, note how many are moving and record the total amount of semen in the cup. This is your pre-wash sperm count.

The technician will then take that semen sample and prepare it for use in the IUI. There are two main techniques used for semen preparation – swim up method and density gradient separation. In a swim up, a test tube filled with a sperm-friendly fluid is placed on top of the semen. Healthy sperm cells will swim up into the test tube to separate them from the non-usable parts of the semen. In a density gradient separation, multiple layers of fluids with different densities are placed in a tube and the semen is layered on top. The tube is then spun in a centrifuge. Healthy sperm cells are filtered through the layers of fluid and end up at the bottom of the tube while everything else is left at the top. Studies show that both methods are effective ways to isolate healthy sperm cells for use in an IUI.

Following the sperm prep, the technician will take a drop of the post-wash sample and place it on a slide noting the number of sperm cells and the % motility. They will record this as the post-wash sperm count. Ideally, there should be more than 1 million total motile sperm cells post-wash.

Are motility and morphology important for IUI?

For an IUI, motility and count need to be considered together. Motility is often reported as a percentage. Without knowing the count, it is impossible to know if the motility is “good” for an IUI. Some clinics will do the math for you and report a total motile sperm count (TMSC). If they don’t, you can use the equation above to calculate it yourself.

Morphology is a different beast all together. Morphology is a measurement of how many sperm “look” normal. Some examples of abnormal sperm include sperm with two tails, two heads, large heads or misshapen heads. Surprisingly, most sperm are abnormally shaped and there are lots of debates about how important sperm morphology is for natural conception or for an IUI.

There are some genetic conditions that can cause all the sperm to have the same deformity, such as globospermia. In these cases, a morphology examination can reveal that sperm are unable to fertilize an egg on their own and ICSI would be recommended. These cases are generally rare and would show up on a semen analysis as 0% normal morphology and a deeper analysis would likely be recommended.

For most people, morphology is reported as a % normal and average is around 15% normal. It is general practice for clinics to look for at least 4% normal sperm when evaluating male fertility. Literature confirms that success rates of IUI are higher in men who have at least 4% normal sperm. However, morphology is only a single piece of the puzzle, methods for measuring it vary from lab to lab and the usefulness of the 4% normal cut-off is highly debated. So, when deciding on fertility treatment options, the entire case should be considered and discussed with your doctor.

What factors are most important to know if an IUI will be successful?

The baseline success rate for an IUI cycle is about 12%. Some factors that have been shown to improve the success rate are:

  • Woman’s age: Women under 30 have better chances of success
  • Semen quality: Total Motile Sperm Count above 5 million, greater than 4% normal have greatest likelihood of success
  • For stimulated cycles: Ideally two follicles bigger than 16mm and estrogen higher than 500pg/mL on the day of trigger shot
  • Timing: IUI occurring 12 – 36 hours after trigger shot and 10-15 minutes of rest following insemination.

How many cycles of IUI are recommended?

There aren’t any strong medical guidelines around the number of cycles of IUI a couple should try. Studies show that there is merit in attempting more than one IUI cycle as the cumulative success rate increases as you add additional cycles.

One review paper examined 3,714 couples who had undergone a total of 15,303 treatment cycles to try to determine if there was an optimal number of cycles to recommend. They found that it could be worth considering up to 9 cycles of IUI. In that study, 7.4% of couples were pregnant after 1 cycle,  18% were pregnant after 3 cycles, 30% after for 6 cycles, and 41% after 9 cycles. While the total chance of conceiving increased as couples added cycles, the chances of each additional cycle being successful was lower than the previous one. So there is usefulness in adding additional cycles, but not indefinitely.

Like everything related to fertility, deciding if you should get an IUI and how many IUI cycles you should consider is a complicated, emotional question. Science can provide some insight to help with decision making but ultimately the call is up to you. Here are some things to think about if you are considering multiple IUI cycles:

Time trying to conceive: How long have you been trying and how old are you? How healthy are you? Can you take steps to improve your fertility to get pregnant naturally? Is age against you?

Cause of infertility: Do you have a known cause? Is it something that IUI can help overcome?

Financial: Are you paying out of pocket for treatment? Will insurance cover IUI cycles? How much does IUI cost compared to other fertility treatments?

Insurance: Sometimes coverage may allow or mandate a certain number of cycles before IVF is reimbursed.

Natural vs Stimulated: Stimulation meds can have side effects and often have a limit of how many back-to-back cycles can be performed without a break for recovery. If you are planning on using medication with your cycle, it would be good to discuss this with your doctor.

Emotional: Negative pregnancy tests are devastating, especially when going through treatment. Planning the number of cycles you would like to attempt ahead of time can reduce the heartache associated with a negative result in the first cycle and can also help you have peace around moving on to other options.

References

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Ruiter-Ligeti J1, Agbo C2, Dahan M3. The impact of semen processing on sperm parameters and pregnancy rates after intrauterine insemination. Minerva Ginecol. 2017 Jun;69(3):218-224. doi: 10.23736/S0026-4784.16.04002-8. Epub 2016 Dec 16.

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Sara SDx

Sara SDx

Editor of Don't Cook your Balls, Co-Founder of TrakFertility.com, Health Coach and Men's Health Advocate. Passionate about sperm, men's health and helping people build their families.

4 Comments

  1. reshma March 2, 2018 at 2:48 pm - Reply

    Hi Sara,

    I am trying to conceive from few months, we are having intercourse regularly also going under follicular scan, this month scanning is complete, for the reference below are the details:

    Uterus-normal size
    endometrial thickness-13mm
    small echogenic area in the upper segment endometrium(post menstratution scan advised for confirmation)
    multiple small follicles noted in bilateral ovaries
    right ovary follicle- follicle rupture in minimal internal haemorrhage(last follicle growth-14*17mm and 16*14mm)
    left ovary follicle- same as above(last follicle growth-22*18mm)
    endometrium-13mm
    free fluid- yes

    any possibility to conceive this month my cycle is due on 13 march? also what is “minimal internal haemorrhage”? will I be needing IUI?

    • Sara SDx
      Sara SDx March 2, 2018 at 5:21 pm - Reply

      What did your doctor say?

      • reshma March 4, 2018 at 6:35 pm - Reply

        Doctor said finger crossed for this month 🙂 this is the reason of asking your evaluation, as my husband’s semen analysis report was ok.

  2. Nisha Mehta February 10, 2018 at 12:36 pm - Reply

    Hello,

    I read your Article which more useful for us. There is one more article which will give you important Information About IUI : https://www.elawoman.com/

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