By Anne Harding
But other researchers must confirm the findings before any general recommendations can be made about taking fish oil during pregnancy, Dr. Sjurdur F. Olsen of Statens Serum Institut in Copenhagen, the study's lead author, told Reuters Health.
In 1990, Olsen and his team randomly assigned 533 pregnant women to take the equivalent of 2,7 grams of omega-3 fatty acids in fish oil capsules, olive oil capsules, or nothing, every day for their last 10 weeks of pregnancy. On average, the women taking the fish oil had pregnancies that were four days longer and infants who weighed 100 grams more compared with the other groups.
The researchers re-evaluated 523 of these children when they were 16 years old to determine whether fish oil influenced the risk of asthma and related conditions. They used information from a registry that records all reported diagnoses from hospital contacts for Danish citizens.
Nineteen of the children given fish oil or olive oil had been diagnosed with asthma by age 16, while 10 had been diagnosed with allergic asthma. Those whose mothers had taken fish oil were 63 percent less likely to have asthma, and 87 percent less likely to have allergic asthma.
Rates of asthma and allergic asthma among children born to women who weren't instructed to take fish or olive oil capsules during pregnancy were similar to those for children whose mothers took fish oil; this was likely because they decided to take fish oil on their own initiative, Olsen and his colleagues suggest.
There is "substantial evidence" laboratory studies that omega 3 fatty acids can affect immune system components that have been implicated in the development of immune diseases, notes Olsen, who is also adjunct professor of nutrition at Harvard. But given the small numbers of children with asthma in the current study, the findings must be interpreted cautiously and confirmed by larger studies, he added in an interview.
Olsen's group is now conducting an observational study of 70 000 pregnant women who gave birth between 1997 and 2003, as well as a trial in seven European countries that is also funded by the European Union through its Early Nutrition Programming Project.