Straight fish oil recommended in pregnancy to reduce pre-term births
Pregnant women are being urged to double-check their intake of omega-3 and not rely on multivitamins after a review found strong evidence additional intake reduces the risk of preterm labour.
An updated Cochrane review this month concluded that omega-3 long chain fatty acid addition during pregnancy – usually by supplementation – reduced the risk of preterm birth (<37 weeks) by 11% (95% CI 0.81-0.97).
The intervention was even more effective at preventing early preterm birth (<34 weeks), with a 42% risk reduction (95% CI 0.44 to 0.77). It was also found to reduce the risk of having a low birth weight baby by 10% (95% CI 0.82 to 0.99).
Review lead author, Professor Maria Makrides of the Healthy Mothers, Babies and Children research program at the South Australian Health and Medical Research Institute, said the findings were “extremely promising”.
“We now have strong evidence that omega-3 supplements are a simple and cost-effective intervention to prevent premature birth,” she said.
Professor Makrides urged women to take straight fish oil or algal oil capsules to get the required dose of omega-3 to prevent preterm births.
“The best available evidence from the randomized controlled trials in the review suggest that the minimum effective dose is 500 to 1000 mg per day of DHA and EPA (eicosapentaenoic acid), with at least 500mg coming from DHA,” she told doctorportal.
Professor Makrides cautioned that women were unlikely to achieve the recommended dose by dietary means – equivalent to two or three 150g servings of salmon weekly.
She also warned that popular pregnancy multivitamins usually did not contain enough omega 3 fatty acids – in particular, docosahexaenoic acid (DHA) – to be protective. Typical formulations only provided women with 250mg of DHA daily.
“Although many women take a pregnancy multivitamin, most of the evidence would suggest that there is no need for most of them,” she said. “Aside from this recommendation regarding fish oil, the only other evidence-based supplement routinely recommended in pregnancy is folic acid between peri-conception and 12 weeks to prevent neural tube defects”.
The latest review was the second update of the original 2006 review. It considered 70 randomised controlled trials assessing the impact of omega-3 on a range of maternal, neonatal and birth outcomes in women of varying risk profiles.
Professor Makrides said it was unclear from the evidence whether the dosage to prevent preterm births should vary by baseline omega-3 status or for multiple pregnancies.
‘Dampening down’ the birth trigger
Interest in omega-3 fatty acid supplementation in pregnancy began in the 1980s, after Danish researchers observed longer pregnancies among Faroe Islanders – who consume a diet high in fish – than in the mainland Danish population.
Cochrane review co-author Associate Professor Philippa Middleton told doctor portal: “Omega-3 fatty acids, and particularly DHA, are thought to reduce or dampen down the potency of prostaglandins that may otherwise have triggered early birth.”
The potential adverse consequence of this effect – going overdue – was evident in the latest review. Prolonged gestation >42 weeks was “probably increased from 1.6% to 2.6%” in women taking omega-3 supplements compared with those who did not, the review found (RR 1.61 95% CI 1.11 to 2.33).
However, the review found there was insufficient evidence to determine the effects of omega-3 on induction post-term.
Professor Middleton commented: “Overdue labour was a previous concern, but practice has now changed and very few women reach 42 weeks now without being induced.”
She added: “Women could stop taking the supplement at 37 weeks if they wished but it’s probably just easier to advise taking until birth.”
Overall, Professor Middleton said there did not appear to be any risks with omega-3 supplements in pregnancy.
Cognitive benefits not clear
In the past decade, observational studies have fueled claims that fish oil may improve children’s cognition and reduce the risk of maternal depression when taken in pregnancy.
However, the authors of latest Cochrane review update downgraded their assessment of the quality of evidence for this association.
One of the major studies to challenge the suggested cognitive benefits of fish oil in pregnancy was led by Professor Makrides in 2010. The five-year randomised controlled trial of 2400 pregnant Australian women found no evidence that fish oil reduced the risk of post-natal depression. The study also found no evidence that the supplement improved child cognition or language development at 18 months of age.
The Cochrane team concluded that further follow-up of completed trials was needed to assess longer-term outcomes for mother and child.