Fertility depends on a surprisingly wide range of factors, many of which are within your control. Age is the single biggest variable, but diet, body weight, environmental exposures, and everyday habits like smoking and caffeine intake all play measurable roles in how quickly you conceive. Here’s what the evidence actually shows, and what you can do with it.
Age Sets the Baseline
Before age 30, a woman has roughly an 85% chance of conceiving within one year of trying. That drops to 75% at age 30, 66% at 35, and 44% at 40. These numbers reflect egg quality and quantity, both of which decline steadily over time. Men’s fertility also declines with age, though more gradually, with measurable drops in sperm quality typically beginning in the early 40s.
The American Society for Reproductive Medicine recommends that couples under 35 try for 12 months before seeking a fertility evaluation. If the woman is 35 or older, that window shortens to 6 months. For women over 40, earlier evaluation is often warranted. These timelines exist because earlier intervention gives you more options.
Diet Makes a Measurable Difference
A Mediterranean-style diet, rich in vegetables, whole grains, fish, olive oil, and legumes, is the most studied dietary pattern for fertility. The results are striking. In one study of women undergoing fertility treatment, those with the highest adherence to a Mediterranean diet had a 50% clinical pregnancy rate compared to 29% among those with the lowest adherence. Live birth rates followed the same pattern: 49% versus 27%.
Across multiple studies, high Mediterranean diet scores were associated with roughly 1.4 to 2.6 times higher odds of pregnancy or live birth. These findings come primarily from women undergoing assisted reproduction, but the underlying biology applies broadly. The diet provides antioxidants that protect eggs and sperm from oxidative damage, healthy fats that support hormone production, and nutrients like folate and zinc that are essential for reproductive function.
You don’t need to overhaul your kitchen overnight. The practical shift is toward more fish, vegetables, nuts, and olive oil, and away from processed foods, refined carbohydrates, and trans fats.
Body Weight and Ovulation
Both ends of the weight spectrum disrupt fertility. A BMI under 18.5 often causes irregular menstrual cycles and can stop ovulation entirely. A BMI in the obese range (over 30) also leads to irregular cycles and ovulatory problems. The sweet spot for reproductive health is a BMI between 19 and 24, though women in the overweight range (25 to 29) can conceive without difficulty in many cases.
If you’re significantly over or under that range, even modest changes help. For women who are overweight, losing 5 to 10% of body weight can restore regular ovulation. For women who are underweight, gaining enough to resume regular periods is often all that’s needed. The goal isn’t a number on a scale; it’s providing your body with enough energy and hormonal balance to support a pregnancy.
Male Fertility Is Half the Equation
About 40 to 50% of infertility cases involve a male factor, yet it’s frequently overlooked. Sperm health is defined by concentration (at least 39 million per ejaculate), motility (at least 42% moving), and morphology (at least 4% normal shape). Several lifestyle factors directly influence all three.
Smoking reduces sperm density by 13 to 17%. Men whose mothers smoked during pregnancy carry an even larger burden: a 20% reduction in sperm concentration and a 24.5% reduction in total sperm count. Heat exposure is another significant factor. Regular sauna use can reduce sperm counts by up to 50%. The good news is that heat-related damage is highly reversible. In one study, men who stopped regular hot tub or hot bath exposure saw their motile sperm counts increase by an average of 491% within three months.
For men trying to conceive, the basics matter: avoid excessive heat to the groin (hot tubs, saunas, laptops directly on the lap), quit smoking, and follow the same dietary principles that benefit female fertility.
Timing Intercourse Correctly
You have a fertile window of roughly five to six days each cycle: the five days before ovulation and the day of ovulation itself. Identifying that window accurately makes a real difference.
Urinary LH test strips (ovulation predictor kits) are the most practical tool. They detect the hormone surge that triggers ovulation, and in clinical testing they reached 97% accuracy with near-perfect sensitivity. A positive result predicts ovulation within about 20 hours on average, giving you a reliable 24 to 48 hour window to time intercourse.
Basal body temperature tracking, by contrast, is far less reliable. The temperature shift that signals ovulation only aligned with the actual LH surge within one day in just 22% of cycles. Experts no longer recommend BBT as a primary method for couples trying to conceive. If you’re choosing one method, LH strips are significantly more useful.
Caffeine, Alcohol, and Smoking
Caffeine in moderate amounts appears safe. The current recommendation for women trying to conceive is to limit intake to the equivalent of one to two cups of coffee per day. Going above that hasn’t been definitively linked to infertility, but higher consumption is associated with longer time to conception in some studies.
Alcohol is more straightforward. The recommendation is to avoid it entirely when trying to conceive and during pregnancy. Even moderate drinking has been associated with reduced fertility in both men and women, and there’s no established safe threshold during the preconception period.
Smoking is unambiguous. It damages egg quality, accelerates the loss of ovarian reserve, and as noted above, significantly reduces sperm quality. Quitting is one of the single most impactful changes either partner can make.
Environmental Chemicals to Reduce
A class of chemicals called phthalates, found in plastics, personal care products, and food packaging, can interfere with reproductive hormones in both men and women. They disrupt the signaling system that controls the release of hormones essential for ovulation and sperm production. In men, certain phthalates block the action of testosterone at the cellular level. In women, they can interfere with estrogen and progesterone signaling and impair placental function.
BPA, found in some plastic containers and can linings, acts similarly. You can reduce your exposure by avoiding microwaving food in plastic containers, choosing fragrance-free personal care products, storing food in glass or stainless steel, and opting for fresh foods over heavily packaged ones. These steps won’t eliminate exposure entirely, but they meaningfully reduce the dose your body absorbs.
Supplements Worth Considering
CoQ10 is the supplement with the strongest evidence for fertility, particularly for women over 35. It works by supporting the energy-producing structures inside egg cells (mitochondria), which naturally become less efficient with age. CoQ10 stabilizes these structures, boosts energy production, and reduces markers of cell damage in both eggs and the surrounding cells.
Clinically studied doses range from 200 mg per day for women with normal ovarian reserve to 600 mg per day for women with diminished ovarian reserve. In reviews of clinical trials, supplementation at these levels increased clinical pregnancy rates in women undergoing fertility treatment. Supplementation is typically started 30 to 90 days before trying to conceive, since egg maturation takes about three months.
Folate (or folic acid) is universally recommended for women trying to conceive, primarily because it prevents neural tube defects, but it also supports healthy cell division during early pregnancy. A standard prenatal vitamin covers this, along with vitamin D and iron, which are commonly deficient and relevant to reproductive health.
Putting It All Together
Fertility isn’t determined by any single factor. It’s the cumulative effect of dozens of inputs, many of them under your direct control. The changes with the largest impact are also the most straightforward: eat more whole foods and fewer processed ones, reach a healthy weight, stop smoking, limit alcohol, track ovulation with LH strips rather than guessing, and for men, avoid regular heat exposure to the groin. If you’re over 35, consider adding CoQ10 and don’t wait longer than six months before seeking evaluation if you haven’t conceived. These aren’t dramatic interventions. They’re adjustments that, taken together, can meaningfully shift the odds in your favor.