Therefore the U.S. Food and Drug Administration and the U.S. Environmental Protection Agency suggested that pregnant women should consume less than 12 ounces of fish in their diet per week. However the National Healthy Mothers, Healthy Babies Coalition is now claiming that restricting fish consumption to the recommended levels can be harmful to the baby.

The coalition includes groups like the American Academy of Pediatrics and the March of Dimes, the National Institute of Child Health and Human Development and the Centers for Disease Control and Prevention. Therefore their recommendations do carry weight.
The group says that consuming fish leads to improved cognitive and motor skills as well as better brain development in babies. Omega-3 fatty acids like docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are essential for the neural development in fetuses and by reducing fish consumption; mothers were depriving their babies of these nutrients.

Newslocale.org examined several international studies on fish consumption and pregnancy. Given below are some such studies.

Prenatal mercury exposure and blood pressure in childhood

A study by researchers at the University of Rochester School of Medicine and Dentistry examined whether prenatal methyl mercury exposure from fish consumption affected blood pressure in childhood.

The researchers used data from the Seychelles Child Development Study (SCDS). The authors note that there were reports of significantly increased diastolic and systolic blood pressure in 7-year-old children. For their study they obtained blood pressure at ages 12 and 15 years on children with known prenatal exposure to mercury from fish consumption.

The study did not find any increase in blood pressure prenatal mercury exposure in either sex at the age of 12. However diastolic blood pressure increased in boys with known prenatal mercury exposure at the age of 15. The authors wrote in the June 2007 issue of Neurotoxicology that their finding warranted further study.

Prenatal methylmercury exposure from ocean fish consumption in the Seychelles child development study

Researchers at the National Institute for Child Health and Development, National Institutes of Health and Department of Health and Human Services investigated 779 mother-infant pairs residing in the Republic of Seychelles. Mothers reported consuming fish on average 12 meals per week.

The researchers assessed neurocognitive, language, memory, motor, perceptual-motor, and behavioural functions in children at age 9 years. The researchers found that increased mercury exposure was associated with decreased performance in the grooved pegboard using the non-dominant hand in males. However they found improved scores in the hyperactivity index of the Conner's teacher rating scale.

Writing in the May 17, 2003 issue of The Lancet, the authors concluded, "These data do not support the hypothesis that there is a neurodevelopmental risk from prenatal mercury exposure resulting solely from ocean fish consumption."

Maternal seafood consumption in pregnancy and neurodevelopmental outcomes in childhood (ALSPAC study)

Researchers at the US National Institute on Alcohol Abuse and Alcoholism and the US National Institutes of Health used data from the Avon Longitudinal Study of Parents and Children (ALSPAC) "to assess the possible benefits and hazards to a child's development of different levels of maternal seafood intake during pregnancy."

Some 11,875 pregnant women participated in the study and answered a food frequency questionnaire that concerned seafood consumption at 32 weeks' gestation.

The researchers found that eating less than 340 g of seafood per week resulted in a decrease verbal intelligence quotient (IQ) in children as compared to children of mothers who ate more than 340 g of seafood per week.

"These results show that risks from the loss of nutrients were greater than the risks of harm from exposure to trace contaminants in 340 g seafood eaten weekly," the authors conclude in the February 17, 2007 issue of The Lancet.

Fish intake during pregnancy and mercury level in cord and maternal blood at delivery: an environmental study in Poland.

Researchers from the Epidemiology and Preventive Medicine, Collegium Medicum, Jagiellonian University, Kopernika in Poland estimated the amount of absorbed mercury by mothers and their infants as a result of fish consumption during pregnancy.

The study involved 313 mother-infant pairs and assessed the level of mercury in cord and maternal blood. Writing in the International Journal of Occupational Medicine & Environmental Health, the researchers conclude, "Fish eating in pregnancy significantly contributes to prenatal mercury exposure."

As is evident from the above studies there are mixed views on whether fish consumption during pregnancy is advisable or not. A recent study in the American Journal of Preventive Medicine says that would-be mothers should not totally avoid fish, but should stay away from shark, king mackerel, swordfish and tilefish, which contain high levels of mercury.