For pregnant women, supplements of the omega-3 fatty acid docosahexaenoic acid (DHA) may help to reduce the likelihood of giving birth very prematurely, according to a new study.
The results add to evidence that omega-3 fatty acid supplements make pregnancy last a little longer. That’s important for women in the U.S., who have shorter pregnancies and lower birth weights, on average, than in many other developed countries, lead author Susan Carlson told Reuters Health.
“It didn’t reduce all preterm births, but reduced the riskiest preterm births,” said Carlson, a nutritionist at the University of Kansas Medical Center in Kansas City.
Carlson and her colleagues recruited 350 women between eight and 20 weeks pregnant and gave them either a supply of capsules, each containing 200 mg of algae-derived DHA, to take three times a day until giving birth, or placebo.
Ultimately, women taking the DHA supplements tended to have slightly larger, heavier babies and to give birth about three days later than the placebo group.
Though there was little difference in the number of preterm births in both groups, the placebo group had considerably more births of very early preemies, according to results published in the American Journal of Clinical Nutrition.
Five percent of mothers in the placebo group had their babies at less than 34 weeks, compared to less than 1% in the omega-3 group.
The researchers credit DHA with the differences because they measured fatty acid levels in mothers’ and babies’ blood, and found that only the DHA-supplemented mothers had raised DHA compared to the study’s outset, and DHA was the only fatty acid whose level had changed.
DHA, an essential fatty acid, can’t be manufactured in the body and must be obtained by eating cold water oceanic fish. It is included in some prenatal vitamins and can be bought as a supplement on its own, costing about $30 for a bottle of 180 capsules, 500 mg each.
Though studies haven’t found clear, consistent benefits for fetal brain development, as researchers once hoped, the evidence for prolonging pregnancy is sound.
“This one adds another brick to the foundation,” Dr. Emily Oken, of the department of population medicine at Harvard Medical School in Boston, who was not involved in the study, told Reuters Health.
“It seems that one of the very few consistent effects of fish oil and other marine oil supplementation in pregnancy is to increase duration of pregnancy by 2-3 days,” according to Maria Makrides, professor of human nutrition at the University of Adelaide in Australia.
A previous study in Mexico that used 400 mg per day did not lead to longer pregnancies. The newest results may indicate that at least 600 mg is necessary for the beneficial effect, Makrides told Reuters Health by email.
Birth before 34 weeks is one of the leading causes of infant death, Oken said, so these results are “definitely reason for enthusiasm.”
Women in the U.S. tend to avoid fish during pregnancy because of the mercury, which can impair brain and nervous system development for the baby, so they may be missing out on some important nutrients, like DHA, selenium and protein, Carlson said.
“We shouldn’t discount the benefits of eating fish,” up to two times per week during pregnancy, Oken said. Pregnant women should just avoid fish high in mercury, like swordfish, tilefish, mackerel and shark.
Am J Clin Nutr 2013.
— Kathryn Doyle1