Fish are often recommended during pregnancy as a healthy protein source, but many mothers-to-be are concerned about reports that many fish species have mercury contamination that can harm a developing baby. In general, the key to consuming fish during pregnancy is to know which species are safest to eat and how much to eat to maximize the benefits while reducing the risk of mercury toxicity.
Methylmercury
Mercury in fish gets there as a result of absorption from the water and from consumption of other organisms contaminated with mercury. The form of mercury in fish is methylmercury, which forms when bacteria alter environmental mercury that falls from the air into a water source such as a lake, pond or ocean. Methylmercury accumulates in the muscle tissue of fish, so longer-living fish tend to have more of it.
Mercury's Health Effects
Methylmercury consumed by a pregnant woman can cross the placenta and affect the developing baby. A fetus of a woman who consumes a lot of mercury may encounter future motor and language development problems. Mercury can also affect the areas of the brain involved in memory and attention and could damage the developing baby's eyesight.
Fish Health Benefits
The decision to not eat fish during pregnancy isn't clear-cut, however. Fish are a good source of lean protein during pregnancy and also contain high levels of omega-3 fats. The omega-3 fats in fish, DHA and EPA, help promote proper brain and eye development in the fetus. As the Baby Center website notes, pregnant women who eat more fish may have a lower risk of preterm birth and low-birth-weight babies. Infants also exhibit better motor and cognitive skills at 6 and 18 months if their mothers consumed fish during pregnancy.
Types of Fish
Almost all fish have some mercury contamination, but some have much higher levels than others. King mackerel, swordfish, tilefish, shark, grouper, marlin and orange roughy have the highest levels of mercury and should be banished from a pregnancy diet. Fish that should be limited during pregnancy because of high levels of mercury include saltwater bass, ahi tuna, white albacore tuna, sea trout, bluefish and halibut. Fish with moderate levels of mercury include carp, mahi-mahi, cod, skate, snapper, herring, freshwater perch, skate, Pacific albacore tuna and canned chunk light tuna. The lowest levels of mercury are found in anchovies, pollock, catfish, butterfish, flounder, haddock, salmon, sole, tilapia, freshwater trout, farmed sturgeon and sardines.
Recommendations
In general, the benefits of fish outweigh the risks of mercury contamination as long as pregnant women make smart choices about the type of fish they consume, explains the American Pregnancy Association. Fish with the highest levels of mercury should be avoided completely during pregnancy. Fish with high mercury should be limited to three or fewer 6-oz. servings each month. Pregnant women should consume no more than six 6-oz. servings per month of fish with moderate levels of mercury. Fish low in mercury can be eaten up to twice a week in 6-oz. servings.
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