IUI success rate and male factors: sperm characteristics

Last Updated on November 27, 2020

Intrauterine insemination (IUI) is a first line fertility treatment before proceeding to in-vitro fertilization (IVF). It involves “washing” the sperm and transferring the concentrated sperm directly into a female’s uterus. This way, the distance that sperm have to travel significantly shortens, thereby increasing the chance of fertilizing an egg in the fallopian tubes.

According to the American Society for Reproductive Medicine, IUI is often recommended when there is:

  • Mild male infertility, such as low sperm count and difficulty ejaculating
  • Donor sperm is used
  • Mild endometriosis
  • Problems with ovulation
  • Cervical stenosis or abnormalities
  • Unexplained infertility

The success rate for IUI is affected by many factors. On the male side, IUI is affected by sperm quality and quantity.


IUI Success rate by sperm count

In the latest 2019 report published on the Fertility Research and Practice, there were 312 pregnancies out of 2062 IUI cycles, resulting in a 15.1% pregnancy rate per cycle and 35.9% per couple.1 For women under the age of 35, the pregnancy rate significantly reduced when the number of motile spermatozoa inseminated (post-wash) is under 5 million. However, when maternal age exceeds 35 years old, sperm count is not a good predictor of success.

A study involving 672 IUI cycles compared the semen parameters of pregnant and non-pregnant subjects.2 The researchers found that progressive sperm count may be a better indicator than motile sperm count, which accounts for only sperm that can swim in a mostly straight line instead of very tight circles. As the total progressive sperm count increases, the clinical pregnancy rate increased. When the initial (pre-wash) progressive sperm count was lower than 5 million, no pregnancy was achieved at the end of the third cycle.

Recommended minimum sperm count thresholds for IUI

Recommended minimum sperm count thresholds for IUI vary in the literature, with reports of 1 million, 2 million, 5 million and 10 million. These discrepancies are likely due to different semen preparation methods and cause of infertility.

A systematic review published in the Journal of Reproductive Biomedicine examined 55 studies on the relationship between semen quality and IUI success. The following semen parameters could be used to attempt IUI:3

  • Pre-wash sperm count > 5 million
  • Post-wash sperm count > 1 million
  • Sperm morphology > 4%
  • Total motility > 30%

Nevertheless, the authors warned that the quality of evidence was low. Meeting these criteria do not necessarily guarantee success and vice versa. There are other factors that also determine success rate, including the use of ovarian stimulation protocols and follicle characteristics. Sperm counts are also not perfect predictors of fertilizing potential because biochemical defects are not reflected in numbers.

Donor sperm IUI success

Donor sperm is commonly used to conceive in same-sex female couples and single parents. Generally, females with no fertility issues using donor sperm can have the highest IUI success rate. In a 2017 study including 1264 IUI cycles with frozen donor semen, the clinical pregnancy rate per cycle was 17.2%.4 None of the post-thaw sperm quality parameters, including sperm count and motility affected the pregnancy rate. The most predictive indicator for pregnancy success is the female age, which significantly decreases when age increases. Factors that were beneficial to IUI success were:

  • Young maternal age
  • Use of ovarian stimulation protocols
  • Lower progesterone levels on day 0 of cycle
  • Low dose ovarian stimulation protocols


1. Minimize the time intervals from semen collection to IUI

Different IVF clinics have different protocols regarding semen collection and sperm wash. Some patients are told to bring a semen sample from home, while others go to the clinic for semen collection. A study of 132 cycles reported that semen collection at the clinic results in higher IUI success rate (44%) as compared to collection at home (18%).5 Immediate semen processing within 30 minutes of collection results in a higher success rate (48%) as apposed to the 18% after 30 minutes. Similarly, the success rate drops again if IUI is performed after 90 minutes of semen collection. Therefore, the time intervals between semen collection to sperm wash, and from sperm wash to IUI should be minimized as much as possible.

2. Short abstinence period

While longer abstinence is correlated with higher sperm count, it is detrimental to sperm motility. A study of 929 cycles showed that the highest pregnancy rate was achieved with an abstinence period of 3 days or less (14%).6 By contrast, the lowest pregnancy rate is associated with more than 10 days of abstinence (3%). A more recent study also supports shorter period of abstinence, and reports the highest pregnancy rate in abstinence of less than 2 days.7

3. Gentle sperm preparation method

There are a few different sperm preparation (washing) methods, and you should aim to find a clinic that uses the least disruptive preparation. For example, wash or swim-down methods are better than density gradient column that requires multiple rounds of centrifugation.8 Centrifugation has been shown to damage the sperm membrane and reduce IUI success.

4. Consider IVF when total mobile sperm count is below 5 million

Despite a lack of consensus on the best sperm indicator for IUI success, most studies report low or no chance of pregnancy when the total motile sperm count is below 5 million. There is a high likelihood that morphology and biochemical properties of the sperm are also affected in extremely low sperm count. Therefore, it could save money and time by proceeding to higher level assisted reproductive technologies when sperm count is lower than 5 million.

5. Optimize other factors affecting IUI

There is still a great deal of debate regarding how important semen characteristics are for IUI success. There is some evidence that other female factors such as the number of follicles and ovarian stimulation protocols are more important determinants of IUI success.9

How many IUI cycles do you need?

One review paper examined a total of 15,303 IUI cycles and found that 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 success rate increased with more cycles, the chances of each additional cycle being successful was lower than the previous one. Therefore, although success rate can increase up to 9 cycles, 3 cycles is generally the number recommended before moving on to IVF or intracytoplasmic sperm injection (ICSI). For patients with more severe infertility factors, including a low ovarian reserve, it is often worth proceeding to IVF earlier.


1 Gubert, P. G., Pudwell, J., Van Vugt, D., Reid, R. L. & Velez, M. P. Number of motile spermatozoa inseminated and pregnancy outcomes in intrauterine insemination. Fertil Res Pract 5, 10, doi:10.1186/s40738-019-0062-z (2019).

2 Zhang, E., Tao, X., Xing, W., Cai, L. & Zhang, B. Effect of sperm count on success of intrauterine insemination in couples diagnosed with male factor infertility. Mater Sociomed 26, 321-323, doi:10.5455/msm.2014.26.321-323 (2014).

3 Ombelet, W., Dhont, N., Thijssen, A., Bosmans, E. & Kruger, T. Semen quality and prediction of IUI success in male subfertility: a systematic review. Reprod Biomed Online 28, 300-309, doi:10.1016/j.rbmo.2013.10.023 (2014).

4 Thijssen, A. et al. Predictive factors influencing pregnancy rates after intrauterine insemination with frozen donor semen: a prospective cohort study. Reprod Biomed Online 34, 590-597, doi:10.1016/j.rbmo.2017.03.012 (2017).

5 Yavas, Y. & Selub, M. R. Intrauterine insemination (IUI) pregnancy outcome is enhanced by shorter intervals from semen collection to sperm wash, from sperm wash to IUI time, and from semen collection to IUI time. Fertil Steril 82, 1638-1647, doi:10.1016/j.fertnstert.2004.04.061 (2004).

6 Jurema, M. W. et al. Effect of ejaculatory abstinence period on the pregnancy rate after intrauterine insemination. Fertil Steril 84, 678-681, doi:10.1016/j.fertnstert.2005.03.044 (2005).

7 Marshburn, P. B. et al. A short period of ejaculatory abstinence before intrauterine insemination is associated with higher pregnancy rates. Fertil Steril 93, 286-288, doi:10.1016/j.fertnstert.2009.07.972 (2010).

8 Dickey, R. P. et al. Decision to do IUI or IVF–sperm count? Fertil Steril 76, 1086-1087, doi:10.1016/s0015-0282(01)02530-4 (2001).

9 Erdem, A., Erdem, M., Atmaca, S., Korucuoglu, U. & Karabacak, O. Factors affecting live birth rate in intrauterine insemination cycles with recombinant gonadotrophin stimulation. Reprod Biomed Online 17, 199-206, doi:10.1016/s1472-6483(10)60195-2 (2008).