Fertility improves most when you address the basics: body weight, diet, timing of intercourse, and reducing exposures that damage eggs or sperm. Some of these factors have surprisingly large effects. Women who closely followed a Mediterranean-style diet, for example, had nearly double the pregnancy rate compared to those with the lowest adherence. Here’s what the evidence shows makes the biggest difference.
Body Weight and Conception Odds
A BMI between 18.5 and 24.9 is the range most strongly associated with healthy fertility. Once BMI climbs above that, the effect on conception is measurable and consistent: for ovulatory women, the chance of spontaneous conception drops by about 5% for every single BMI point above normal. Women with a BMI of 32 or higher have roughly 2.7 times the risk of anovulatory infertility, meaning their bodies are less likely to release an egg at all.
Being underweight matters too. A BMI below 18.5 can disrupt hormone signaling enough to stop ovulation. UK fertility guidelines recommend a BMI of 29 or lower as the ideal threshold for women trying to conceive, but the strongest outcomes cluster closer to the normal range. If your weight is significantly above or below that window, even a modest shift of 5 to 10 percent of body weight can restore regular ovulation for many women.
Timing Intercourse to the Fertile Window
The fertile window is roughly five days long, ending on the day of ovulation. The daily probability of conception rises sharply starting about seven days after the first day of your last period, peaks around day 15 at about 13%, and drops back to zero by day 25. The highest likelihood of being inside your fertile window occurs around day 12 of your cycle, when there’s about a 58% chance that any given day falls within it.
In practical terms, this means having intercourse every one to two days in the week leading up to expected ovulation gives you the best coverage. Ovulation predictor kits, which detect a hormone surge 24 to 36 hours before the egg is released, can help you narrow the window. Tracking basal body temperature confirms ovulation after the fact, which is useful for learning your personal pattern over several cycles.
Diet Quality Has a Large Effect
A Mediterranean-style eating pattern, built around vegetables, fruits, whole grains, fish, olive oil, and legumes, is the most studied dietary approach for fertility. Among women undergoing IVF, those with the highest Mediterranean diet scores had a 50% clinical pregnancy rate compared to 29% in the lowest-scoring group. Live birth rates followed the same pattern: 49% versus 27%. Even outside of IVF, higher diet quality has been linked to a 40% increase in the odds of clinical pregnancy.
The effect appears strongest in women under 35. What likely drives it is the combination of antioxidants, healthy fats, and anti-inflammatory compounds found throughout this style of eating. You don’t need to follow a rigid plan. Prioritizing whole foods over processed ones, choosing fish and poultry over red meat, and using olive oil as your primary fat source captures most of the benefit.
Folic Acid and Supplements
Every woman who could become pregnant should take 400 micrograms (mcg) of folic acid daily. This is a well-established recommendation from the U.S. Public Health Service, primarily because folic acid prevents neural tube defects in early pregnancy, often before a woman knows she’s pregnant. Many prenatal vitamins include this amount, so check the label before adding a separate supplement.
Beyond folic acid, no single supplement has strong enough evidence to be universally recommended for female fertility. Vitamin D deficiency has been associated with lower conception rates, so correcting a known deficiency is reasonable. But megadosing on fertility supplement blends is unlikely to help and can sometimes interfere with other nutrients.
What Improves Male Fertility
Sperm quality is responsible for roughly half of all fertility struggles, so what the male partner does matters just as much. The full cycle of sperm production takes about 64 days, which means any lifestyle change needs at least two to three months before it shows up in a semen analysis.
Heat is one of the most potent and underappreciated threats to sperm. Testicles need to stay 2 to 4°C cooler than core body temperature for normal sperm production, and each 1°C increase in testicular temperature reduces sperm production by about 14%. Saunas, hot tubs, laptops placed directly on the lap, prolonged sitting (six or more hours a day), tight underwear, and electric blankets all raise scrotal temperature enough to impair sperm motility and count. Switching to loose-fitting boxers, taking breaks from sitting, and avoiding regular hot tub use are simple changes with real effects.
Antioxidant supplements have shown some benefit for men with low sperm parameters. Zinc supplementation has been linked to improvements in sperm motility and total normal sperm count. Selenium combined with vitamin E produced measurable improvement in sperm motility or shape in over half of participants in one trial. CoQ10, taken at 200 mg daily for six months, improved sperm motility and density in some studies, though results have been inconsistent. These supplements are most likely to help men who already have suboptimal semen analysis results rather than those with normal counts.
Alcohol, Caffeine, and Lifestyle Habits
Alcohol has a clear, dose-dependent effect on fertility. Women who drink more than seven alcoholic drinks per week are about 7% less likely to conceive. When a male partner drinks that same amount, the chance of a live birth drops by 9%. Lighter drinking (a few drinks per week) hasn’t shown the same harm in most studies, but cutting back or stopping entirely removes the risk.
Caffeine, surprisingly, does not appear to reduce the odds of pregnancy or live birth for either partner. Moderate coffee consumption (roughly two to three cups per day) has not been linked to fertility problems in the best available analyses. If you enjoy coffee, there’s no strong reason to eliminate it while trying to conceive, though many clinicians suggest capping intake at around 200 mg per day once pregnant.
Smoking is consistently harmful to both egg and sperm quality. It accelerates egg loss in women and damages sperm DNA in men. Quitting improves fertility outcomes within a few months.
Lubricants Can Slow Sperm Down
Most commercial lubricants, and even saliva, reduce sperm motility. If you use lubricant during intercourse, look for products that are hydroxyethylcellulose-based, which most closely match the consistency of natural cervical mucus without impairing sperm movement. Avoid lubricants with fragrances or parabens. Household oils like coconut oil should also be avoided, as they haven’t been tested for sperm safety and can alter vaginal pH.
How Long Changes Take to Work
For women, improvements to ovulation from weight loss or dietary changes can appear within one to three menstrual cycles, though the timeline varies. For men, the 64-day sperm production cycle means you should maintain any changes for at least three months before expecting to see results. This is true for everything from quitting smoking to reducing heat exposure to starting a supplement. Couples who make changes together and sustain them for a full three-month window before reassessing give themselves the best odds.