Women who regularly eat fish during the late stages of pregnancy appear to be less likely have a low-birth weight infant, according to new study findings published on Thursday.

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.

To investigate whether fish intake influences fetal growth, Rogers of the University of Bristol and her team asked more than 11,000 women at 32 weeks of pregnancy how much fish they ate, then noted their babies’ birth weights.

On average, women ate almost 33 grams of fish each day, equivalent to one third of a small can of tuna.

Rogers told Reuters Health that the reasons why fish may help fetuses grow remain unclear. Fish contains omega-3 fatty acids, she said, which may boost blood flow to the placenta, bringing more nutrients to the fetus.

Rogers and her team report their findings in the Journal of Epidemiology and Community Health.

SOURCE: Journal of Epidemiology and Community Health, June 2004.