Many everyday habits can quietly lower your chances of getting pregnant each cycle. Some are well known, like drinking alcohol, while others are surprising, like taking ibuprofen around ovulation or using the wrong lubricant. Here’s what the research actually shows about the habits, substances, and choices worth changing when you’re trying to conceive.
Alcohol Lowers Your Odds More Than You Think
Even moderate drinking reduces your probability of conceiving in any given cycle. A study following couples planning their first pregnancy found a clear dose-response relationship: women who drank just one to five alcoholic beverages per week were 39% less likely to conceive per cycle compared to non-drinkers. At six to ten drinks per week, the reduction was 45%. At eleven to fifteen drinks, it reached 66%. These numbers held up after adjusting for smoking, BMI, and other fertility-related factors.
Alcohol disrupts reproductive hormones, can interfere with ovulation, and is linked to higher rates of irregular periods. There’s no established “safe” threshold for fertility purposes, and even light social drinking appears to make a measurable difference.
Too Much Caffeine Can Work Against You
You don’t need to quit coffee entirely, but the amount matters. Women consuming 200 to 300 mg of caffeine per day (roughly two standard cups of coffee) had about 1.7 times the risk of infertility compared to women drinking under 100 mg. At 400 mg or more per day, the risk jumped to 3.4 times higher. High caffeine intake during early pregnancy is also associated with a 35% increased risk of miscarriage at doses above 300 mg daily.
Keeping your intake under 200 mg per day is a reasonable target. Remember that caffeine adds up from multiple sources: tea, energy drinks, chocolate, and some supplements all contribute.
Common Painkillers Can Block Ovulation
This one catches many people off guard. Over-the-counter anti-inflammatory painkillers like ibuprofen and naproxen (NSAIDs) can inhibit ovulation. These drugs work by blocking the production of prostaglandins, which are essential for the follicle to rupture and release an egg. Research across multiple species consistently shows that NSAIDs taken during the days leading up to ovulation can prevent or disrupt that release.
If you need pain relief around your fertile window, acetaminophen (Tylenol) is generally considered a safer alternative since it doesn’t have the same effect on prostaglandin synthesis. For chronic pain conditions that require regular NSAID use, it’s worth discussing timing strategies with your provider.
The Wrong Lubricant Damages Sperm
Most common lubricants are harmful to sperm. The main culprit is glycerin, the primary ingredient in popular water-based brands like KY Jelly and Durex. Glycerin can penetrate sperm membranes, dissolve the tail’s outer layer, and significantly reduce motility. If you need lubrication during your fertile window, look for products specifically formulated without glycerin and designed to match the body’s natural osmolality. Pre-Seed is the most studied of these and has shown the least negative effect on sperm motility and survival.
Cannabis Use Delays Ovulation
Marijuana use affects both partners’ fertility. In women who smoked cannabis at least once in the previous three months, ovulation was delayed by an average of 1.7 to 3.5 days compared to non-users. That delay can throw off your entire fertile window if you’re timing intercourse based on a typical cycle. Even more striking: 43% of confirmed cycles where no egg was released at all occurred in marijuana users, despite those users making up only 15% of the study population.
For men, smoking marijuana more than once a week was associated with a 29% reduction in total sperm count. Sperm shape and swimming ability weren’t affected in that particular study, but the drop in count alone is significant when you’re trying to maximize your chances.
Intense Exercise Can Backfire
Moderate exercise supports fertility, but pushing into high-intensity territory has the opposite effect for women, even those at a healthy weight. Research shows that two hours of vigorous exercise per week was associated with a 16% lower chance of becoming pregnant compared to sedentary women. At three to four hours weekly, the reduction was 27%. At five or more hours, it reached 32%.
This applies to vigorous exercise specifically, such as running, HIIT, heavy lifting, or intense cycling. Walking, yoga, swimming at a moderate pace, and similar activities don’t carry the same risk. If you’re currently training hard, scaling back intensity rather than quitting altogether is typically enough.
High-Sugar Diets Disrupt Ovulation
A diet heavy in processed sugar and refined carbohydrates can push your body toward chronically elevated insulin levels. That excess insulin directly interferes with ovarian function: it causes premature changes in the cells surrounding developing eggs, leading to disrupted or absent ovulation. Hyperinsulinemia also impairs the uterine lining, potentially making implantation harder even when an egg is released and fertilized.
This isn’t limited to women with polycystic ovary syndrome. Obesity in general correlates with anovulation, and insulin resistance is a key mechanism. Reducing added sugars, choosing whole grains over refined ones, and pairing carbohydrates with protein or fat to slow the blood sugar response are practical steps that support more regular ovulation.
Heat Exposure Matters for Male Partners
Sperm production requires temperatures slightly below core body temperature, which is why the testicles sit outside the body. Regular exposure to heat sources can impair that process. Hot tub or hot bath use three or more times per month was associated with a 13% reduction in the probability of conception per cycle. Animal studies show that testicular temperatures of 43°C (about 109°F) for just 20 minutes trigger cell death in developing sperm.
Frequent laptop use on the lap, prolonged sitting (ten or more hours daily), and heated car seats used more than three hours per week are all potential contributors. Switching to a desk for the laptop, taking movement breaks, and skipping the hot tub during the months you’re actively trying are simple changes worth making.
Watch Your Vitamin A Intake
Vitamin A in its active form (retinol, found in supplements and some skincare products) poses a real risk during the preconception period. Doses above 10,000 IU per day are considered potentially harmful to early fetal development, and the danger is highest in the first 60 days after conception, often before many people even know they’re pregnant. Very high intake (above 25,000 IU daily) has been linked to urinary tract malformations.
Beta-carotene from fruits and vegetables is converted to vitamin A in the body only as needed, so food sources like sweet potatoes and carrots aren’t a concern. The risk comes from high-dose retinol supplements, cod liver oil (which can contain very concentrated amounts), and prescription retinoid skincare products like tretinoin or isotretinoin. Check your prenatal vitamin to make sure the vitamin A it contains is primarily beta-carotene rather than preformed retinol.
Household Chemicals Worth Reducing
Phthalates, a class of chemicals found in plastics, food packaging, personal care products, and building materials, act as hormone disruptors. Higher levels of phthalate byproducts in the body have been linked to decreased ovarian reserve, meaning fewer eggs available for fertilization. Exposure happens through eating, breathing, and skin absorption, making it nearly impossible to avoid completely.
You can meaningfully reduce your exposure by choosing fragrance-free personal care products (synthetic fragrances are a major source), avoiding microwaving food in plastic containers, storing food in glass or stainless steel, and checking labels for “phthalate-free” on items like lotions and shampoos. These changes won’t eliminate exposure entirely, but they reduce the daily load your body has to process.