Fermented foods and preterm birth risk from a prospective large cohort study: The Japan Environment and Children's study

Background: The dietary pattern of pregnant women is known to be associated with preterm birth (PTB). We investigated whether PTB was associated with intake of fermented food by using data from the Japan Environment and Children's Study. Methods: From a data set of 103,099 pregnancies, 77,667 cases at low risk for PTB were analyzed. The primary outcome measurements were based on PTB. Fermented food (miso soup, yogurt, cheese, and fermented soybeans) consumption was assessed by using a semi-quantitative food frequency questionnaire. Results: Intake of miso soup, yogurt, and fermented soybeans before pregnancy significantly reduced the risk of early PTB (< 34 weeks). The adjusted odds ratio (OR) for early PTB in women who had miso soup 1-2 days/week, 3-4 days/week, or ≥ 5 days/week were 0.58, 0.69, and 0.62, respectively, compared with those who had miso soup < 1 day/week (95% confidence interval (CI) 0.40-0.85, 0.49-0.98, and 0.44-0.87). The adjusted OR for early PTB in women who ate yogurt ≥ 3 times/week was 0.62 (95% CI, 0.44-0.87) compared to those who ate yogurt < 1 time/week. The adjusted OR for early PTB in women who ate fermented soybeans ≥ 3 times/week was 0.60 (95% CI, 0.43-0.84) compared to those who ate < 1 time/week. However, the incidence of overall PTB and late PTB (34-36 weeks) was not associated with fermented food intake. Conclusion: PTB low-risk women with a high consumption of miso soup, yogurt, and fermented soybeans before pregnancy have a reduced risk of early PTB.