The journey of trying to conceive (TTC) involves many lifestyle considerations, with diet often becoming a central focus. Advice for the preconception phase is frequently confused with the strict dietary rules of confirmed pregnancy. This period requires a balanced approach to nutrition, prioritizing beneficial elements like Omega-3 fatty acids while minimizing potential risks. The safety of eating sushi, which involves raw fish and concerns about mercury, is a common question for individuals preparing for pregnancy. Understanding the differences between pre-conception and pregnancy guidelines is important for making informed choices about food safety and nutritional intake.
Sushi Safety During the Conception Period
Eating low-mercury sushi from a reputable source is generally not prohibited while trying to conceive. During the preconception phase, the developing embryo is not yet reliant on the maternal blood supply, meaning the risk of immediate harm from a foodborne pathogen is lower than in an established pregnancy. However, the goal of TTC is to create the healthiest possible environment, which involves reducing unnecessary risks.
The main concerns—methylmercury and foodborne illness—must still be managed cautiously. The Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) recommend that women who are or may become pregnant consume 8 to 12 ounces of low-mercury fish per week for its nutritional benefits, emphasizing Omega-3 fatty acids for reproductive health. Therefore, consumption should focus on selecting safe fish types and prioritizing quality over absolute avoidance.
Understanding Mercury Levels in Fish
The primary chemical concern is methylmercury, a potent neurotoxin that accumulates in the body. This heavy metal can cross the placenta and potentially affect the developing nervous system of a fetus. Since methylmercury has a long half-life, estimated at about two months, limiting exposure in the months leading up to conception is important. Avoiding high-mercury fish during the TTC phase helps ensure the body’s levels are low before pregnancy is established.
The FDA and EPA classify fish based on mercury content to help consumers make safer choices. The “Best Choices” category includes low-mercury fish that can be safely eaten two to three times a week, providing beneficial protein and Omega-3s.
Low-Mercury “Best Choices”
- Salmon
- Shrimp
- Cod
- Canned light tuna
- Tilapia
These options are often used in cooked or vegetarian sushi rolls. Conversely, high-mercury fish should be strictly avoided during the preconception period. These include swordfish, shark, king mackerel, and Gulf of Mexico tilefish.
Certain types of tuna used in sushi, like Bigeye and Yellowfin tuna, have higher mercury content. Canned white (albacore) tuna intake should be limited to one serving (about six ounces) per week, and Bigeye tuna is best avoided entirely. Selecting low-mercury varieties like salmon and limiting medium-mercury fish consumption are important steps to mitigate risk.
Raw Fish and Foodborne Illness Risk
Raw fish consumption carries a risk of foodborne illnesses from pathogens such as Listeria monocytogenes and parasites like Anisakis. While these risks exist for everyone, an infection in the earliest stages of pregnancy can potentially interfere with implantation or lead to complications. Listeriosis can cause severe illness in adults and is a significant concern during pregnancy due to the risk of miscarriage or stillbirth.
For those trying to conceive, minimizing this biological risk through quality control is key. Only consume raw fish from highly reputable establishments that adhere to strict food safety standards. “Sushi-grade” fish has typically been frozen to kill common parasites, but this process does not eliminate all bacteria, including Listeria. Opting for cooked sushi rolls, such as those with fully cooked shrimp or eel, eliminates the risk associated with raw fish entirely.
Minimizing exposure to these pathogens is a reasonable precaution during the TTC phase. Focus on rolls that use low-mercury, cooked seafood or vegetables, or ensure any raw fish comes from a source with impeccable food handling practices to reduce the chance of illness.
Dietary Changes Once Pregnancy Is Confirmed
Upon receiving a positive pregnancy test, dietary guidelines immediately become more restrictive to protect the developing fetus. Immune system changes during pregnancy increase susceptibility to foodborne illnesses like listeriosis, which can have devastating consequences. Therefore, all forms of raw or undercooked fish, including all sushi containing raw seafood, must be strictly avoided.
This strict avoidance also extends to other raw or unpasteurized foods that carry Listeria risk, such as unpasteurized juices, soft cheeses, and deli meats. Furthermore, while low-mercury fish remains beneficial, the rules for high-mercury fish become absolute: shark, swordfish, king mackerel, and tilefish must be eliminated from the diet. Continued consumption of low-mercury, cooked fish, such as salmon and shrimp, provides Omega-3 fatty acids that support fetal brain and eye development.