Newborn babies are bigger if mothers eat fish

British researchers are reporting that fish appears to boost the weight of newborn babies.

The findings, which contradict previous studies linking consumption of fish oil to longer pregnancies but not bigger babies, add "to the evidence that fish is an important part of the human diet," said study co-author Imogen Rogers, a researcher at University of Bristol in England.

However, a U.S. environmental watchdog organization continues to advise American women to stay away from most fish if they're pregnant or thinking about having a child. The risk from mercury in the fish is just too large, contends the Washington D.C.-based Environmental Working Group.

Indeed, the U.S. government advises pregnant women and young children to avoid a number of types of fish, including shark, swordfish, king mackerel, and tilefish, reports forbes.com

According to .reuters.com a group of British investigators found that the infants of women who ate no fish while pregnant had a 37-percent higher chance of being very small for their stage of development, a condition known as intrauterine growth retardation (IUGR), than the infants of women who ate the most fish.

Study author Dr. Imogen Rogers warned that more research is needed before it can be recommended that all pregnant women boost their fish intake. "However, (the results) reinforce the current advice given to pregnant women in the UK, which is to eat two portions of fish a week, including one portion of oily fish," she noted.

Rogers added that some fish contains high levels of mercury, which can damage the fetus' developing nervous system if eaten in high quantities. She recommends that women who are pregnant or trying to become pregnant should avoid eating marlin and swordfish and limit their intake of tuna, all of which contain high levels of mercury.

"However, most fish contain relatively low levels of mercury, and the potential dangers of low-level mercury consumption need to be balanced against other potential benefits of eating fish," she said.

However, a diet rich in fish seemed to boost the foetal growth rate in pregnancy. The more fish the women ate, the lower were the rates of restricted foetal growth.

Although this association was not as strong when other influential factors - such as smoking - were taken into consideration, it was still significant.

Restricted foetal growth normally occurs in one in 10 pregnancies, but in women who ate no fish this increased to around one in eight (13%), inform BBC.