New Study Raises Concern about Fish Consumption During Pregnancy

by Jennifer Wider, M.D.

(Washington DC:  4/17/03):  Pregnant women need to pay close attention to their consumption of fish, according to a new study published in the April 2nd Journal of the American Medical Association (JAMA). Approximately 8 percent of the women in the study had levels of mercury in their bloodstreams high enough to cause damage to developing fetuses.

Researchers analyzed the results of interviews, physical exams and blood work performed on women and children who participated in the National Health and Nutrition Examination Survey between 1999 and 2000. While most people surveyed had harmless blood levels of mercury, roughly 8 percent of women had concentrations higher than those deemed safe by the US Environmental Protection Agency (EPA).

According to the JAMA study, fish consumption is one of the primary sources of mercury in the body. Mercury occurs naturally in the environment but can also be produced by industrial activities; as it is absorbed in the soil and water, it can become transformed into different substances that can be toxic to the human body. One of the byproducts, methylmercury, accumulates easily in fish and studies have shown that it can damage the human brain and nervous system, especially in developing fetuses.

"In general, pregnant women or those who intend to become pregnant should not eat swordfish, shark, tilefish or king mackerel," according to Susan Schober, PhD, lead researcher and senior epidemiologist at the National Center for Health Statistics, US Centers for Disease Control and Prevention. These particular types of fish contain high levels of mercury. In addition, Dr. Schober says, "Women should limit their fish consumption to no more than 12 ounces per week."

There are trace amounts of mercury in almost all species of fish. The consumption of fish is an essential part of the diet, even during pregnancy. It is important that women do not eliminate fish from their diets completely because it is a good source of protein and is low in fat.

According to Dr. David Acheson, Chief Medical Officer at the US Center for Food Safety and Applied Nutrition, larger, predatory fish accumulate the highest levels of mercury. "Small creatures on the ocean floor ingest the methylated mercury and are in turn, eaten by larger creatures. The mercury content (in the fish) gets more concentrated as it goes up the food chain," explains Dr. Acheson. Therefore, pregnant or nursing women can safely fill the 12 ounces per week quota with cooked, smaller, and varied types of fish. A serving size ranges from three to six ounces, so women should judge accordingly.

Dr. Schober encourages women to refer to the US Food and Drug Administration (FDA) guidelines regarding fish consumption during pregnancy. She also encourages women to pay close attention to state and local advisories about mercury and fish in their areas. "Concentrations vary widely, but there is enough fish available so women can limit themselves to fish with lower concentrations," Schober adds. According to the FDA, shellfish, canned fish and smaller ocean fish are among the varieties that are safe to consume.

The Society for Women's Health Research is the nation's only not-for-profit organization whose sole mission is to improve the health of women through research. Founded in 1990, the Society brought to national attention the need for the appropriate inclusion of women in major medical research studies and the resulting need for more information about conditions affecting women. The Society advocates increased funding for research on women's health, encourages the study of sex differences that may affect the prevention, diagnosis and treatment of disease, and promotes the inclusion of women in medical research studies. Dr. Donnica Moore has been a member of the Society since 1990 and is a past member of its Board of Directors.

Created: 4/17/2003  -  Jennifer Wider, M.D.
Reviewed: 4/19/2003  -  Donnica Moore, M.D.