Examining the Effect of Fish Oil Supplementation in Chinese Pregnant Women on Gestation Duration and Risk of Preterm Delivery

Sjurdur F Olsen, Thorhallur I Halldorsson, Min Li, Marin Strøm, Yanyan Mao, Yan Che, Yu Wang, Fengxian Duan, Jørn Olsen, Weijin Zhou

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16 Citations (Scopus)


Intervention studies have shown that long-chain (LC) n-3 PUFA intake can prolong gestation but the dose−time−effect relations remain unresolved.

We examined the effect on gestation duration of 2 doses of supplemental LC n-3 PUFAs.

We undertook a 3-group parallel randomized controlled trial in areas of China with low (median: 2.1 g/d) and higher (14.3 g/d) fish intake. Unselected women (median: age, 26.2 y; BMI, 20. kg/m2) were randomly assigned at midgestation to take four 0.72-g identical gelatin capsules per day until the last day of the preterm period (<259 days of gestation), when they were asked to stop. Capsules contained fish oil [high fish oil (HFO) group (60% w/w LC n-3 PUFAs)], a 1:3 mixture of fish oil to olive oil [low fish oil (LFO) group (20%)], or olive oil [control (CON) group (0%)], providing 2.0, 0.5, and 0 g/d of LC n-3 PUFAs, respectively. Habitual fish intake was recorded at baseline. Hazard rate ratios (HRRs) for spontaneous delivery <259 days of gestation and <273 days of gestation across groups were estimated by Cox regression.

Among 5531 women randomly assigned, 92.5% were included in analyses (1706/1825, 1695/1851, and 1717/1855, respectively). The groups were similar with respect to hazard rates <259 days of gestation [HRR: 1.04 (95% CI: 0.70, 1.53) for LFO compared with CON and 0.90 (95% CI: 0.60, 1.35) for HFO compared with CON], hazard rates <273 days of gestation [HRR: 1.00 (95% CI: 0.86, 1.18) and 0.91 (95% CI: 0.77, 1.07), respectively], and mean gestation durations [differences: 0.2 d (95% CI: −0.5, 0.8) and 0.6 d (95% CI: −0.06, 1.2), respectively]. Inspection of pregnancy survival curves suggested that LC n-3 PUFAs delayed delivery in low fish consumers by 5–10 d and that this effect ceased rapidly after stopping taking the capsules.

This trial could not substantiate that fish oil prevents preterm birth in Chinese women, possibly because statistical power was too low. This trial was registered at clinicaltrials.gov as NCT02770456.
Original languageEnglish
Pages (from-to)1942–1951
Number of pages10
JournalThe Journal of Nutrition
Issue number11
Publication statusPublished - 1 Nov 2019


  • China
  • fish oil
  • gestation duration
  • long-chain n-3 fatty acids
  • pregnancy
  • preterm birth
  • RCT


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