Daily consumption by women of 600 milligrams docosahexaenoic acid (DHA) -- an omega-3 fatty acid found in prenatal vitamins, fish-oil supplements and fish -- can prevent high blood pressure in their children, caused by obesity, suggests a study.

"Prenatal DHA exposure appears to programme the developing foetus to be protected against the blood pressure elevating effects of obesity in childhood," said Susan Carlson, Professor at the University of Kansas. To better understand, the team included over 170 women with low-risk pregnancies in the clinical trial and the children were followed through up to six years.

Half of them were randomly given daily prenatal supplement of 600 milligrams DHA, and the other half a placebo. The findings, published in the JAMA Network Open journal, showed being overweight and obese were associated with the expected higher blood pressure, but not among children whose mothers took DHA.

Obese and overweight children of mothers in the placebo group had a large mean increase of 3.94 mm Hg for systolic BP and 4.97 mm Hg for diastolic BP compared with overweight/obese children of DHA-supplemented mothers. Terming the difference statistically significant, co-author of the report John Colombo, Professor at the varsity, said, "This research is aimed at expectant mothers and paediatricians who wonder what you can do prior to the birth of your child to optimise health and behaviour outcomes."

"The prenatal environment programmes a foetus' metabolism for what to expect in the postnatal environment. Part of DHA's known effects may be in programming cardiac function that preserves normal blood pressure in the case of high postnatal weight gain," he said.

The team believes lower blood pressure at age six might extend beyond childhood. "It is known that blood pressure tracks over time such that people with higher BP early in life are more likely to have higher BP later in life," Carlson said.