Pregnancy can make you crazy sometimes; your cravings can get the better of you but you really need to check if it is safe to consume. After all, everything that goes into your system needs to be checked for its benefits and harmful effects not just for you, but for the fetus as well. Among seafood, tuna is most popular and pregnant women have been warned against it for ages. But what is it in Tuna that prevents pregnant women from engaging in this craving?

Can Pregnant Women Eat Tuna?
Yes, it is safe to consume tuna during pregnancy, but in limited amounts. White tuna (albacore) and light tuna are highly recommended. The risk from consuming too much tuna is the exposure to toxic methylmercury. High levels of mercury in the bloodstream of fetuses pose the risk of damage to their nervous system. The FDA (Food and Drug Administration, US) warns that pregnant and nursing women must limit tuna consumption to 6 ounces a week.
Fresh Tuna During Pregnancy:
Fresh tuna is oily and has great nutritional benefits. When compared to canned tuna, fresh tuna is recommended as it is packed with proteins, vitamins and minerals plus a good source of Omega-3 fatty acids, which aid the brain development in the fetus. It is important to remember that tuna that is undercooked can harbor bacteria. Pregnant women must opt for the ones that are cooked at a temperature of 145 degrees Fahrenheit. Seared tuna may be unsafe and is best avoided. If you are planning to eat out in a restaurant, it is best to go for broiled or baked tuna and be on the safer side.

[Source: https://www.livestrong.com/article/553317-is-seared-tuna-safe-in-pregnancy/]
Canned Tuna During Pregnancy:

Canned tuna is permissible as long it is consumed within limits and does not become the main source of food. The risk of mercury content is a cumulative effect so, 1 can of tuna, to satisfy a craving, can do no harm. However, the problem is it is fewer Omega-3 fatty acids when compared to fresh tuna. You could opt for one which has no added salt. Alternately, you could also rinse it for a couple of minutes to reduce sodium content. However, it is better to be careful at a stage when the brain or the nervous system of the baby is under development. At that time, you want to be extra cautious and avoid anything that might do even a little damage. If you want to opt for canned tuna, make sure you go for Yellowfish, which doesn’t have high levels of mercury. Pregnant women can have about 12 ounces of this variety in a week. Light and Albacore are high on mercury levels, so they should be limited to not more than 6 ounces a week.
How Much Tuna is Safe During Pregnancy?
As already mentioned, the FDA has given specific guidelines on safe fish intake and has specified levels for fishes that are permissible for pregnant women. As far as tuna is concerned, it is:

• • 12 ounces/ week of canned, light tuna (these are low in mercury).
  • 6 ounces/week of fresh or canned albacore tuna (these have high mercury levels).

According to the FDA, pregnant women are allowed 8 to 12 ounces of seafood a week. If you happen to consume other seafood, make sure you avoid having tuna the same week.
Can I Eat Tuna From Subway When I’m Pregnant?
Not really. The fact that it is kept out, sometimes uncovered, makes it not just unsafe but unhealthy as well. If you are really craving for it, make sure it is heated before you consume it.
Most seafood are a rich source of Omega-3 fatty acids,  Vitamin B, Iodine, Selenium and Vitamin D. Studies show that they are highly essential to aid the brain development in the baby. Dietary guidelines are prescribed so that you know how to eat healthy, especially when you are pregnant.
The reason why many doctors ask you to avoid higher quantities of tuna is due to the high levels of mercury in the fish. Besides, it also contains environmental pollutants like dioxins and polychlorinated biphenyls (PCBs). When consumed for a long time, these could build up in your body and hamper baby’s development. The whole idea is, you should not restrict yourself to tuna alone, but have a variety of seafood. Always remember to consult your doctor to know exactly what is good for you and what has to be avoided. During pregnancy you are normally advised to have everything in moderation and not go overboard. After all, the food cravings need to be satisfied too, especially during pregnancy, right? Go ahead…stay safe and enjoy your pregnancy.