IUI Low Morphology: What You Need to Know

Starting a family can sometimes feel harder than expected, especially when you learn your partner experiences low sperm morphology (abnormal sperm shape). If you're worried about how this affects your chances of pregnancy using IUI, you're not alone – many couples have the same concern. 

The good news is, sperm shape is only one factor affecting fertility. Sperm count, movement, and timing of the IUI procedure all play important roles, and understanding these factors can help you make informed decisions about your fertility journey.

What is sperm morphology?

Sperm morphology refers to the shape and structure of sperm (how sperm look under a microscope). A healthy sperm cell usually has:

• An oval head

• A normal midpiece (the section behind the head)

• A long tail

On the other hand, abnormal sperm morphology may involve large or small heads, bent tails, or even two heads or tails. These changes can make it harder for sperm to swim properly or reach and fertilise the egg.

To identify these abnormalities, most clinics use Kruger's strict criteria, which involve checking for imperfections in sperm shape and size during a semen test.

What is considered low morphology?

Low morphology (teratozoospermia) occurs when a smaller percentage of sperm has the ideal shape needed for fertilisation. However, it does not automatically mean you can't become pregnant.

The percentage of sperm that are normally shaped is interpreted as follows:

• Normal morphology has 4% or more normal forms in a semen sample (under Kruger strict criteria)

• Low morphology has less than 4% normal forms in a semen sample

Can IUI work with low sperm morphology?

Yes, intrauterine insemination (IUI) can still work when sperm morphology is low, especially if sperm concentration and movement (sperm motility) are normal or close to normal.

IUI helps by placing sperm directly into your uterus (womb), giving them a shorter path to the egg. However, when morphology is very low, other sperm fertility factors become even more important, such as:

• Total motile count (TMC):

  • Measures the total number of sperm that are actively moving in a semen sample.

  • It combines volume, sperm count, and motility (movement) to show how many sperm are likely to reach the egg.

• Progressive motility:

  • Measures how well sperm swim forward in a straight line or large circles.

  • This movement is important because sperm must travel from the uterus to the fallopian tubes to fertilise the egg.

• Sperm DNA fragmentation:

  • Measures the damage or breaks in the sperm’s genetic material (DNA).

  • Even sperm that look normal under a microscope can have DNA damage, which can affect fertilisation and embryo development.

How does IUI help when morphology is low?

IUI can improve your fertilisation chances by removing weaker or misshapen sperm and using only the healthiest ones for the insemination process (placing sperm directly into your uterus).

• Sperm washing:

  • IUI selects the healthiest and most normally shaped sperm and puts them in a concentrated sample. This increases the chances of sperm reaching the egg.

• Direct placement into the womb:

  • The sperm are placed past the cervix (the lower part of the uterus that connects to the vagina), which some abnormally shaped sperm may struggle to pass on their own.

• Timing with ovulation:

  • The procedure is done when your egg is ready, ensuring that more healthy sperm are present at the right time for fertilisation.

Overall, IUI is usually recommended when at least 1-4% of sperm are normally shaped and the total motile count after sperm washing is 5-10 million or more. This means there are enough healthy and moving sperm to reach the egg, which improve the chances of fertilisation.

When might IUI not be recommended?

While IUI can be effective for many couples, IUI may not work well if there are other male or female fertility factors that make it hard for sperm to reach the egg. It is less likely to succeed when:

• Very few sperm (less than 1%) have the right shape for fertilisation

• Sperm DNA damage is high, which can affect embryo development

• There are a female fertility issues, such as blocked fallopian tubes or poor egg quality

• You've already experienced several failed IUI cycles, usually more than 3 well-timed attempts

In these situations, your doctor may recommend IVF (in vitro fertilisation) or ICSI (intracytoplasmic sperm injection) instead. These assisted reproductive technologies (ART) help the sperm meet or enter the egg directly, thereby avoiding problems caused by poor sperm shape or movement.

How can you improve sperm health?

Other than medical treatments, lifestyle changes can also play a significant role. Some causes of poor morphology are genetic, but many relate to lifestyle. Because sperm takes about 2 to 3 months to mature, maintaining healthy habits over time can improve sperm quality.

Ways your partner can support healthy sperm:

• Avoid smoking and alcohol

• Eat a balanced diet and maintain a healthy weight

• Take antioxidants such as vitamins C, E, zinc, CoQ10, and folic acid

• Avoid heat exposure such as in hot tubs, saunas, and tight underwear

• Reduce contact with pesticides, plastics, and radiation

• Manage stress and get enough sleep

• Keep laptops off your lap for long periods

If you're looking for ways to improve your partner's reproductive health, request an appointment with Thomson Medical's fertility specialists. Our doctors can assess your partner's lifestyle, recommend targeted interventions, and guide you with personalised strategies to optimise sperm quality and support your chances of conception.

FAQ

Should couples with low sperm morphology skip IUI and go straight to IVF?

The idea that couples with low sperm morphology should always skip IUI and go straight to IVF is not always true. In many cases, IUI can still be a reasonable first step, depending on how low the morphology is and other fertility factors.

What factors are more important than morphology for IUI success?

While sperm shape matters, other factors often play a bigger role in IUI success. The total number of motile sperm and how well they swim straight, known as progressive motility, are usually more important. Additionally, the timing of the insemination, as well as your age and egg quality, also affect the pregnancy rates.

What is the minimum sperm morphology required for IUI?

There is no fixed number that applies to everyone. In general, IUI may still be possible when one to two percent of sperm have a normal shape under Kruger strict criteria. Better outcomes are often seen when morphology is four percent or higher, especially when sperm count and movement are also satisfactory.

Does low sperm morphology significantly affect IUI success rates?

Low sperm morphology can affect IUI success if it is extremely low, such as below one percent, and is combined with other sperm problems like a low count. However, when sperm morphology is mildly to moderately low which is between 1-4% and other sperm factors are normal, pregnancy rates are often similar to those of men with normal morphology.

Can sperm morphology improve over time?

Yes, in some cases it can. Healthy lifestyle changes, antioxidant supplements, and time may help improve sperm shape. However, improvements are not guaranteed and usually take about three to four months to assess.

How do I know if IUI is the right option for me?

It is best to speak with your fertility specialist at a fertility clinic. IUI may be suitable when your male partner has mild to moderately low morphology, but other sperm results are acceptable, your fallopian tubes are open, and you ovulate regularly. If there are no severe male factor infertility problems or other health concerns, IUI can be a reasonable first step for you.

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and tailored advice based on your unique situations, please consult a specialist at Thomson Medical.Request an appointment with Thomson Medical today.

References:

Bocu, K., Boeri, L., Mahmutoglu, A. M., & Vogiatzi, P. (2024). Can lifestyle changes significantly improve male fertility: A narrative review? Arab Journal of Urology, 23(3), 190–200. https://doi.org/10.1080/20905998.2024.2421626

Burks, H., Peck, J. D., Hansen, K. R., Stoner, J., & Craig, L. B. (2025). Low morphology does not lower success after intrauterine insemination unless inseminating motile sperm count is low. PLoS ONE, 20(3), e0317521. https://doi.org/10.1371/journal.pone.0317521

Lee, R. K., Hou, J., Ho, H., Hwu, Y., Lin, M., Tsai, Y., & Su, J. (2002). Sperm morphology analysis using strict criteria as a prognostic factor in intrauterine insemination. International Journal of Andrology, 25(5), 277–280. https://doi.org/10.1046/j.1365-2605.2002.00355.x