Several foods and dietary habits can meaningfully reduce your chances of getting pregnant, from ones that disrupt ovulation hormones to others that harm sperm quality in a male partner. Some of these are obvious, like alcohol, while others are surprisingly specific. Here’s what the evidence actually shows.
Trans Fats and Fried Foods
Trans fats are the single most clearly linked dietary factor to ovulatory infertility. A large prospective study from the Nurses’ Health Study found that replacing just 2% of daily calories from carbohydrates with trans fats was associated with a 73% greater risk of ovulatory infertility. Swapping trans fats in place of healthy monounsaturated fats (like olive oil) more than doubled the risk. The mechanism appears to involve insulin sensitivity and a receptor that helps regulate ovulation, meaning trans fats may directly interfere with egg release.
Trans fats are found in partially hydrogenated oils, which still appear in some commercially fried foods, packaged baked goods, microwave popcorn, and certain margarines. While the U.S. has largely phased out artificial trans fats, they haven’t disappeared entirely. Check ingredient lists for “partially hydrogenated” oils, and limit deep-fried restaurant food, which can still be a significant source.
High-Mercury Fish
Fish is genuinely good for fertility (more on that below), but certain species accumulate enough mercury to pose real risks during the conception window and early pregnancy. The FDA identifies seven fish to avoid entirely:
- King mackerel
- Marlin
- Orange roughy
- Shark
- Swordfish
- Tilefish (Gulf of Mexico)
- Bigeye tuna
Mercury is a neurotoxin that accumulates in your body over time, so it’s worth cutting these out well before you conceive, not just once you’re pregnant. Lower-mercury options like salmon, sardines, and shrimp are safe and actually beneficial. Men benefit too: one study found that men who ate the most fish had 65% higher total sperm counts compared to those who ate the least.
Processed Meats
If a male partner is part of the equation, processed meat is worth paying attention to. A study of men attending a fertility clinic found that those who ate the most processed meat (bacon, sausage, hot dogs, deli meats) had 23% fewer normally shaped sperm than men who ate the least. Sperm morphology matters because abnormally shaped sperm have a harder time reaching and fertilizing an egg.
The effect was specific to processed meat rather than all red meat, suggesting that preservatives, nitrates, or the processing itself may be the issue rather than the protein source. Replacing some processed meat with fish appears to work in both directions: improving sperm quality while also providing omega-3 fats that support female fertility.
Sugary Foods and Refined Carbohydrates
Foods that spike blood sugar rapidly can disrupt the hormonal balance needed for regular ovulation. When blood sugar shoots up, insulin follows. Chronically high insulin increases free testosterone in women and reduces a protein called sex hormone-binding globulin, which normally keeps reproductive hormones in balance. Over time, this combination can interfere with egg maturation and ovulation, a pattern closely linked to conditions like polycystic ovary syndrome (PCOS).
The biggest offenders are white bread, sugary cereals, candy, pastries, and sweetened beverages. You don’t need to eliminate all carbohydrates. The distinction is between rapidly digested refined carbs and slower-digesting whole grains, beans, and vegetables that produce a gentler insulin response. Swapping white rice for brown rice or sugary breakfast cereal for oatmeal are practical changes that shift the hormonal picture in the right direction.
Diet Sodas and Artificial Sweeteners
Switching to diet versions of sugary drinks may not be the fix it seems. A study of women undergoing fertility treatment found that consuming any amount of diet soft drinks was associated with lower egg and embryo quality, along with reduced implantation rates. Artificially sweetened coffee showed a similar negative association with embryo development. The study had limitations and didn’t find a difference in live birth rates, but the pattern across multiple markers was consistent enough to take seriously when you’re actively trying to conceive.
Alcohol
Moderate drinking (under 14 servings per week) doesn’t appear to measurably reduce the chance of conceiving in any given cycle, based on a large Danish cohort study. But at 14 or more drinks per week, fecundability, the probability of getting pregnant during a given menstrual cycle, dropped by 18%. That’s a meaningful reduction when you consider it compounds cycle after cycle.
The practical takeaway: a few drinks per week likely won’t delay conception, but regular heavy drinking will. And because most people don’t know the exact moment of conception, many clinicians recommend cutting back substantially or stopping altogether during the months you’re actively trying, since alcohol in very early pregnancy carries its own well-documented risks.
Caffeine in Large Amounts
Caffeine below 200 mg per day does not appear to be a major factor in miscarriage or preterm birth, according to the American College of Obstetricians and Gynecologists. That’s roughly one 12-ounce cup of brewed coffee. Going above that threshold is where the evidence gets murkier, so staying under 200 mg is a reasonable guideline during the preconception period. Keep in mind that caffeine adds up from multiple sources: tea, chocolate, energy drinks, and some sodas all contribute.
Liver and High-Dose Vitamin A
Organ meats, particularly liver, are often promoted as nutrient-dense superfoods. And they are, which is actually the problem. Liver contains extremely high levels of preformed vitamin A (retinol), and too much retinol during the conception window and early pregnancy is toxic to a developing embryo. A single 3-ounce serving of cooked beef liver can contain anywhere from 15,000 to nearly 60,000 IU of vitamin A, depending on the source animal. Research has shown that intake above 10,000 IU per day from supplements, or above 15,000 IU per day from diet, increases the risk of birth defects affecting the head and face.
This doesn’t apply to beta-carotene from vegetables like carrots and sweet potatoes. Your body converts beta-carotene to vitamin A only as needed, so plant sources don’t carry the same risk. The concern is specifically with preformed vitamin A from animal liver and high-dose supplements. If you take a prenatal vitamin, check the label to make sure it contains beta-carotene rather than retinol, or that the retinol dose is well under the 10,000 IU threshold.
Raw and Unpasteurized Foods
Certain foodborne infections are especially dangerous in very early pregnancy, sometimes before you even know you’re pregnant. That’s why food safety guidelines apply during the preconception period, not just after a positive test. Pregnant women are 10 times more likely to contract Listeria than the general population, and infection can cause miscarriage.
Foods to avoid or handle carefully:
- Soft cheeses made from unpasteurized milk (queso fresco, brie, camembert, blue cheese)
- Deli meats and hot dogs unless heated until steaming
- Raw or undercooked eggs, including homemade Caesar dressing, cookie dough, and runny yolks
- Raw sprouts (alfalfa, bean, clover)
- Unpasteurized juice, cider, or raw milk
- Raw fish and shellfish, including sushi, sashimi, and ceviche
- Refrigerated smoked seafood (labeled lox, nova-style, or kippered) unless cooked into a dish
- Premade deli salads like tuna salad, egg salad, and chicken salad
Canned Foods and BPA Exposure
Many canned foods are lined with a resin containing BPA, a chemical that mimics estrogen in the body. California has formally classified BPA as a female reproductive toxicant. Research from Stanford found that canned food consumption directly correlates with urinary BPA levels: the more canned food in your diet, the higher the exposure. While BPA-free cans exist, the replacement chemicals are not always well studied. Choosing fresh, frozen, or foods packaged in glass over canned versions is a simple way to reduce exposure during the months you’re trying to conceive.