The study found that children whose mothers ate fish sticks during pregnancy were twice as likely to develop asthma, whether or not their mothers had asthma themselves. “Fish sticks are deep-fried, and they contain omega-6 fatty acids, which encourage inflammation of the airways,” said study co-author Frank Gilliland, M.D., Ph.D., Professor of Preventive Medicine at the Keck School of Medicine at the University of Southern California in Los Angeles. “Oily fish contain omega-3 fatty acids, which appear to be anti-inflammatory, and lead to the reduced potential for developing asthma and allergies.”

The study found that children whose mothers with asthma ate oily fish during pregnancy were 71% less likely to develop asthma on average; the more oily fish a woman ate, the less likely her child was to develop asthma.

Children with non-asthmatic mothers did not benefit from having their mother eat oily fish during pregnancy

“A family history of asthma is a very strong risk factor for a child developing asthma,” Dr. Gilliland said. “It appears that oily fish interacts with the genes involved in the predisposition to develop asthma, and somehow reduces the risk.”

The children in the study were selected from the Children’s Health Study, a population-based study of school-aged children in 12 Southern California communities. One group of children had physician-diagnosed asthma by age 5, and the other group was asthma-free when the study started. The children’s mothers were interviewed about their diet and other environmental exposures during pregnancy.

“We are learning more and more about the importance of fetal exposure to different substances, and how this affects the programming of the baby’s immune system,” Dr. Gilliland said.