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Background: Intervention studies have shown that long-chain (LC) n-3 PUFA intake can prolong gestation but the dose-time-effect relations remain unresolved.Objectives: We examined the effect on gestation duration of 2 doses of supplemental LC n-3 PUFAs.Methods: 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.Results: 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.Conclusion: 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. [ABSTRACT FROM AUTHOR]

Objective Food frequency questionnaires are relatively inexpensive, easy and quick to administer, but the construction of a food frequency questionnaire that can capture Chinese food habits is challenging given the diverse lifestyle and eating habits in different parts of the country. The aim of this study was to assess the validity and reproducibility of a self-administered food frequency questionnaire against a 3-day dietary recall in a rural region of western China. Design Prospective cohort study. Setting Chinese maternal and child healthcare hospital. Population A total of 168 healthy pregnant women. Methods Pregnant women completed a food frequency questionnaire at 16-24 weeks gestation, and again at 29-31 weeks; during weeks 26-27 they completed a 3-day dietary recall. Results In general, mean intake was higher when assessed with food frequency questionnaires compared with dietary recall. Spearman and intra-class correlation coefficients between the two food frequency questionnaires ranged from 0.31 to 0.69 and from 0.27 to 0.79, respectively. For the second food frequency questionnaire and the dietary recall, the crude and de-attenuated Spearman correlations ranged from 0.12 to 0.55 and 0.14 to 0.58, respectively. The correlation both between the two food frequency questionnaires and between the second food frequency questionnaire and the dietary recall decreased after adjustment for energy. Ranking women, 31-57% and 1-8% were classified into the same and the opposite quartile, respectively, by both food frequency questionnaires; 30-45% and 1-11% were classified into the same and the opposite quartile respectively for the second food frequency questionnaire and dietary recall. Conclusion The food frequency questionnaire showed good reproducibility and correlations with dietary recall; it is useful for ranking study participants according to dietary intake, which is of great importance to future etiological studies in this cohort. [ABSTRACT FROM AUTHOR]