Researchers reviewed 24 years of studies on intrauterine insemination (IUI), a common fertility treatment where sperm is placed directly into the uterus. They found that success depends on many factors: the woman’s age, weight, stress levels, and nutrition; the quality of the sperm; and how the procedure is done. The review shows that when women have healthy BMI, good nutrition (especially certain vitamins and minerals), and avoid smoking and alcohol, pregnancy rates improve. The thickness of the uterine lining, the number of healthy sperm, and the type of hormone stimulation used also matter significantly. This comprehensive look at decades of research helps doctors and patients understand what conditions give the best chances of success.

The Quick Take

  • What they studied: What factors help or hurt the success of intrauterine insemination (IUI), a fertility treatment where doctors place sperm directly into a woman’s uterus to help with pregnancy.
  • Who participated: This wasn’t a single study with participants—instead, researchers looked at hundreds of studies published between 2000 and 2024 involving thousands of couples trying fertility treatments.
  • Key finding: IUI works better when women are at a healthy weight, eat well (with enough vitamins and minerals), manage stress, avoid smoking and alcohol, and have good-quality sperm from their partner. The thickness of the uterine lining and the number of healthy sperm are especially important.
  • What it means for you: If you’re considering IUI, focusing on lifestyle changes like maintaining a healthy weight, eating nutritious foods, reducing stress, and avoiding smoking and alcohol may improve your chances of success. Talk to your doctor about whether these changes are right for you before starting treatment.

The Research Details

This wasn’t a traditional research study with new experiments. Instead, researchers acted like detectives, searching through thousands of published studies from 2000 to 2024 to find patterns and common themes. They looked at many different types of studies—some that randomly assigned people to different treatments, some that followed groups of people over time, and some that compared people who had IUI with those who didn’t. By combining information from all these different studies, they could see which factors consistently helped or hurt IUI success.

The researchers searched major medical databases (PubMed and Google Scholar) to find all the relevant studies. They then carefully reviewed each study to understand what it found about IUI outcomes. This approach, called a narrative review, is useful when you want to understand the big picture across many years of research rather than focus on just one specific question.

This type of review is important because IUI success rates vary a lot from person to person and from clinic to clinic. By looking at 24 years of research all together, scientists can identify the most important factors that make IUI work. This helps doctors give better advice to patients about how to prepare for treatment and what to expect. It also helps identify which lifestyle changes might actually make a difference versus which ones don’t matter as much.

This review is a summary of existing research rather than a new study, so its strength depends on the quality of the studies it reviewed. The researchers looked at many different types of studies, which gives a broad view but also means some studies were stronger than others. Some findings came from small studies with few participants, while others came from larger, more reliable studies. The review notes that some findings are more certain than others, and readers should be cautious about interpreting results from very small studies. The fact that this review was published in a respected medical journal suggests it was carefully reviewed by other experts.

What the Results Show

The research shows that several key factors strongly influence whether IUI will be successful. First, the woman’s age, weight, stress level, and nutrition all matter significantly. Women who maintain a healthy body weight and eat well—especially getting enough unsaturated fats, folate, B12, vitamins A, C, and E, and minerals like zinc and selenium—tend to have better outcomes.

Second, specific measurements during the procedure are important. When the uterine lining (the tissue where a baby would grow) is between 6-10 millimeters thick, pregnancy rates are higher. The quality and quantity of sperm also matters greatly—studies show that having at least 5-10 million motile (moving) sperm after preparation gives better results.

Third, how doctors stimulate the ovaries (using hormones to help produce eggs) affects success. Using gonadotropin-based protocols (a specific type of hormone treatment) appears to work better than other approaches. Finally, avoiding harmful exposures like tobacco, alcohol, and other reproductive toxins improves chances of success, especially when combined with other healthy lifestyle choices.

The review also found that several procedural techniques may help improve outcomes, though the evidence is less certain. These include using soft catheters (thin tubes) during the procedure, performing the insemination slowly rather than quickly, and providing support during the luteal phase (the second half of the menstrual cycle). However, these findings come from smaller studies, so doctors should be cautious about recommending them as standard practice. The number of mature eggs produced and their quality also play a role in success rates.

This review brings together 24 years of research, so it shows how our understanding of IUI has evolved. Earlier studies identified some of these factors individually, but this comprehensive review confirms which factors are most consistently important across many different studies and populations. It also highlights that while we’ve known some factors matter (like sperm quality), we now have better understanding of specific thresholds—like the ideal endometrial thickness of 6-10 mm—that give the best results. The emphasis on lifestyle factors like nutrition and stress management reflects growing recognition that what happens outside the clinic is just as important as what happens inside.

This review has several important limitations to understand. First, it’s a summary of other studies rather than a new study itself, so it’s only as good as the studies it reviewed. Some of the studies included were small, which means their results might not apply to everyone. Second, different studies measured things differently and had different populations, making it hard to compare results directly. Third, some findings came from observational studies (where researchers watch what happens naturally) rather than randomized controlled trials (where people are randomly assigned to different treatments), which are considered more reliable. Fourth, the review notes that some findings should be interpreted cautiously because the evidence is mixed or comes from small studies. Finally, this review was published in early 2026, so it doesn’t include any research published after 2024.

The Bottom Line

Based on this research, if you’re considering IUI, discuss these evidence-based approaches with your fertility doctor: (1) Maintain a healthy body weight before starting treatment—this is supported by strong evidence. (2) Ensure good nutrition, particularly adequate intake of unsaturated fats, folate, B12, and vitamins A, C, and E—this has moderate evidence of benefit. (3) Manage stress through relaxation techniques or counseling—this appears helpful based on multiple studies. (4) Avoid smoking and alcohol—this has strong evidence of improving outcomes. (5) Ask your doctor about using gonadotropin-based hormone stimulation and ensuring endometrial thickness is in the optimal range of 6-10 mm before the procedure. These recommendations should be personalized with your doctor based on your individual situation.

This research is most relevant for couples considering IUI as a fertility treatment, particularly those who are early in their fertility journey. It’s especially important for women who are overweight, have poor nutrition, smoke, or drink alcohol—as these are modifiable factors that might improve outcomes. Men should also pay attention, as sperm quality is a major factor. Healthcare providers offering fertility treatment should use these findings to counsel patients about preparation. However, this research is less relevant for people who have already decided against IUI or those with severe fertility issues that require more advanced treatments. People with specific medical conditions should discuss how these findings apply to their situation with their doctor.

Lifestyle changes like improving nutrition, reducing stress, and quitting smoking typically take 2-3 months to show effects on reproductive health, so it’s best to start these changes at least 3 months before IUI treatment. Weight loss, if needed, should ideally happen over several months rather than quickly. Once you start IUI treatment, you may know within 2-3 weeks if it was successful (through pregnancy tests). If the first cycle doesn’t work, doctors often recommend trying again, and improvements from lifestyle changes may become more apparent over multiple cycles. Don’t expect overnight results—fertility treatment success builds on consistent healthy habits over time.

Want to Apply This Research?

  • Track daily nutrition intake focusing on: unsaturated fats (nuts, fish, olive oil), folate-rich foods (leafy greens, legumes), B12 sources (meat, dairy, fortified foods), and minerals like zinc (shellfish, seeds) and selenium (Brazil nuts, fish). Log weekly weight if working toward a healthy BMI. Record stress levels daily (1-10 scale) and note stress management activities used.
  • Set a specific goal like ’eat 2 servings of fatty fish per week’ or ‘practice 10 minutes of meditation daily’ or ’eliminate alcohol for 3 months before IUI.’ Use the app to set reminders for vitamin/mineral-rich meals, schedule stress-reduction activities, and track progress toward a healthy weight. Create a checklist of pre-IUI preparation tasks with your doctor’s recommendations.
  • Use the app to track the 3-month preparation period before IUI with weekly check-ins on nutrition, stress, weight, and lifestyle factors. During the IUI cycle itself, log any symptoms and procedure details. After treatment, continue tracking to identify patterns if multiple cycles are needed. Share reports with your fertility doctor to discuss which lifestyle factors may have influenced outcomes.

This review summarizes research on intrauterine insemination but is not a substitute for personalized medical advice. IUI success depends on individual circumstances, and what works for one person may not work for another. Before starting any fertility treatment or making significant lifestyle changes, consult with a qualified fertility specialist or reproductive endocrinologist who can evaluate your specific situation. Some findings in this review come from small studies or have mixed evidence, so your doctor may have different recommendations based on current clinical practice and your individual needs. If you’re struggling with fertility, seek professional medical evaluation rather than relying solely on lifestyle changes.