Too much of a good thing can turn bad and this appears to be true when it comes to consuming fish during pregnancy. Although health experts urge pregnant women to eat fish, findings of a new study have shown that having more than three servings of fish in a week may have unwanted effects on the unborn child.  

The study, which was published in JAMA Pediatrics, found that pregnant women who eat more than three servings of fish in a week, which is more than the maximum recommended by health regulators, have increased odds of having babies who grow fast and become obese when they reach 4 to 6 years old.

Leda Chatzi, from the University of Crete in Greece, and colleagues tracked more than 26,000 women and their children observing the kids' growth patterns and weight status until age 6. They found that the children who were born to women who ate fish more than three times weekly had higher BMI values at age 2, 4 and 5 than those of women who ate less fish.

The researchers also observed that high intake of fish during pregnancy was linked to an elevated risk for rapid growth from birth to 2 years old and an increased risk for the children to be overweight or obese by age 4 and 6. The impact was likewise observed to be more pronounced in girls than in boys.

The researchers said that environmental pollutants in fish could be attributed for the link between high intake of fish during pregnancy and elevated risk for childhood obesity.

Mercury poisoning is a primary reason why pregnant women have been eating too little fish prompting public health campaigns to urge them to consume more.  In 2014, the U.S. Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) recommended that pregnant women eat up to three servings of fish per week and steer free of fish that are contaminated with mercury such as king mackerel, shark and swordfish.

The researchers said that the results of their study are in line with the intake limit set by the FDA and EPA. They urged women to continue consuming fish for its important nutrients while adhering to fish consumption guidelines.

Fatty fish such as salmon, tuna and cod are known to contain omega-3 fatty acids, which are crucial for the development of the baby's brain and retinal tissues. These also play a role in warding off women's depression during pregnancy and after birth.

"This large, multicenter study indicates that fish intake of more than 3 times/week in pregnancy is associated with increased risk of rapid growth in infancy and increased adiposity in childhood.," the researchers wrote. "Our findings are in line with the fish intake limit for pregnancy proposed by the US Food and Drug Administration and Environmental Protection Agency."