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THURSDAY, Jan. 28 (HealthDay News) -- Omega-3 fatty acid supplements are believed to have many health benefits, but the one thing they can't do is help women with a history of delivering their babies early carry their next child to full term, new research finds.
"The omega-3 did not add any benefit," said study author Dr. Margaret Harper, an associate professor of obstetrics and gynecology at Wake Forest University School of Medicine, Winston-Salem, NC. The study appears in the February issue of Obstetrics & Gynecology.
Harper and her colleagues randomly assigned 852 pregnant women with a history of a preterm birth either to get a daily omega-3 supplement or a placebo beginning about week 16 to 22 and continuing through week 36 of gestation.
All women also received weekly intramuscular hormone injections of hydroxyprogesterone caproate, which has been shown to improve the chances of carrying a baby to term, Harper said.
Her team followed up to see which women delivered before 37 weeks. Full-term is defined as 37 weeks of completed gestation.
Delivery before 37 weeks occurred in 37.8% of those taking omega-3, and 41.6% of those in the placebo group, a small difference.
Prematurity is the leading cause of newborn death, the authors write in the report, and it is increasing in the United States. A woman who delivers one baby before term is more likely to deliver future babies early.
Harper's team decided to study the value of the omega-3 supplements after conflicting findings about the value of the supplements for women at high risk of premature delivery. For those at low-risk, she said, the findings seem to agree that omega-3 supplements don't further reduce the risk of preterm birth.
A recent large review of published studies found only one that showed benefit of the supplements in high-risk women, she said.
Why did experts think omega-3s might help?
According to Harper, omega-3 fatty acids, when metabolized, are converted to much less potent biochemicals called prostaglandins, which make the uterus contract, than are omega-6 fatty acids -- also essential fatty acids but typically over-eaten in Western diets. Adding omega-3s to an omega-6-heavy diet, so the thinking went, might result in better chances of carrying the baby to term.
But in Harper's study, she also noted that women getting omega-3 supplements were more likely to give birth to a baby with respiratory distress syndrome (RDS). While 59 babies (13.9%) of those in the omega-3 group had RDS, only 35 (8.7%) of those in the placebo group did. In other words, the omega-3 mothers' babies were 1.6 times more likely to get RDS than infants born to mothers taking placebo. It's the first time such a finding has been reported in clinical trials, the authors wrote.
The study is well-done and scientific, said Dr. Ashlesha Dayal, a maternal-fetal medicine specialist at the Montefiore Medical Center in New York City. The results clearly indicate that ''the addition of omega-3 fatty acids did not make a difference in recurrent spontaneous preterm birth," she said.
But should pregnant women ditch omega-3 supplements altogether?
Maybe not, Dayal said. "While the study's results showed no difference, there is early evidence that omega-3 fatty acids are beneficial for fetal brain development, so women should still consider taking them, in conjunction with their doctor's advice, despite what seems to be little benefit for the reduction of spontaneous preterm birth."
Harper disagreed for now. "I think we need more study before we can say definitively that it benefits the fetal brain," she said.
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