Taking fish oil supplement during pregnancy is linked to an increase in infant lean and bone mass by the age of six years, according to Danish and UK researchers.
Overall, they found fish oil supplementation in the later stages of pregnancy was associated with a higher body mass index in children in the first six years of life.
“Body composition in children given fish oil supplementation was characterised by a proportional increase in lean, bone, and fat mass”
But they said this trend was explained by an increase in total lean and bone mass at six years of age, but with no increase in fat mass.
Previous trials had shown that pregnant women with a higher intake of fish oil gave birth to higher birth weight infants, but the impact on children later in life has been unclear, said the researchers.
For the new study, researchers from Bristol University and Copenhagen examined the effect of taking fish oil supplements during pregnancy on the growth and body composition of children later in life.
The trial involved 736 pregnant women who were randomised to receive n-3 long-chain polyunsaturated fatty acids (LCPUFAs) (fish oil) or olive oil (control) daily from week 24 of pregnancy week until one week after birth.
Height, weight, head and waist measurements were assessed 11 times from birth to age six years and adjusted for age and sex.
These revealed a sustained higher BMI from one year to six years of age, said the researchers in the British Medical Journal.
Body composition was assessed using dual-energy X-ray absorptiometry (DXA) scans at 3.5 and six years of age and demonstrated that the higher BMI was not the result of a higher fat percentage.
Instead, it reflected a proportional increase in lean mass, bone mass, and fat mass, which suggested that the fish oil supplementation had a general growth stimulating effect.
At age six, children whose mothers had taken supplements had a 395g higher total mass, 280.7g higher lean mass, 10.3g higher bone mineral content and 116.3g higher fat mass than the controls.
The researchers said: ”Fish oil supplementation from the 24th week of pregnancy led to a higher BMI in the offspring from zero to six years of age but not an increased risk of obesity at age six.
“The body composition at age six years in children given fish oil supplementation was characterised by a proportional increase in lean, bone, and fat mass suggesting a general growth stimulating effect,” they added.