Giving pregnant moms omega-3 fatty acid supplements might help prevent infection in their infants, suggests new research.
But the benefit of docosahexaenoic acid, or DHA, wasn't always obvious, and researchers say not all babies will necessarily be better off because of it.
Boosting mothers' DHA did not produce dramatic effects. "What we did find, however, is a general trend toward benefit," said study author Dr Usha Ramakrishnan, of Emory University in Atlanta.
Studies of the effect of fatty acid supplements on the immune system in kids or adults have shown inconsistent results, the authors said online in Paediatrics.
DHA and the immune systems of infants
Whether giving pregnant women extra DHA could improve their infants' immune systems has been even less clear.
To investigate that question, Dr Ramakrishnan and her colleagues recruited more than 1,000 pregnant women - all four or five months along - receiving prenatal care at a hospital and several health clinics in Cuernavaca, Mexico.
Half the volunteers took two 200-mg DHA supplements each day. The other half took twice-daily placebo capsules containing a blend of corn and soy oils.
Women continued taking the supplements until they gave birth. Then they brought their new babies back to the general hospital in Cuernavaca at one, three, and six months, and reported on the infants' recent sickness symptoms.
DHA babies suffer fewer symptoms
At one month, babies of moms who had taken DHA had a trend toward fewer total cold symptoms than babies of moms who weren't supplemented. About 38% of DHA group babies showed cold symptoms in the couple of weeks before that appointment, compared to 45% of placebo babies. But the difference wasn't statistically significant.
At three and six months, there was no clear distinction between the two groups of babies with regard to cold symptoms. But in babies that did get sick, those whose moms had taken DHA had a shorter duration of some symptoms, such as fever and runny nose.
In a couple of cases, babies of DHA moms had suffered symptoms for longer than comparison babies. For example, at the three-month visit, babies with colds had been stuffed up for an extra day in the DHA group, on average, according to their moms' reports.
Dr Ramakrishnan said that it generally seems safe to take DHA during pregnancy, at least in the doses her team examined. At much higher doses, similar fatty acids have been linked to bleeding risks. The 400-mg daily dose is pretty typical of what would be in a prenatal vitamin or what moms could get in a couple of fish meals each week, she added.
Pregnant women told to limit fish intake
Because of concerns about mercury exposure, the US Food and Drug Administration recommends that pregnant women limit their fish intake to two meals per week, choosing fish and shellfish that are low in mercury, such as salmon and shrimp.
Some studies have also linked omega-3 fatty acids to lower cholesterol and a smaller risk of heart disease. So, should pregnant moms be taking DHA to give their infants an infection-fighting boost?
"I think it may be variable – not everybody may benefit," Dr Ramakrishnan said. When it comes to infants' health, "It's not going to be that magic bullet."
(Reuters Health, July 2011)