Changes in Dietary Intake in Pregnant Women from Periconception to Pregnancy in the Japan Environment and Children’s Study: A Nationwide Japanese Birth Cohort Study

Background: Nutritional requirements increase during pregnancy. However, relatively few studies have examined longitudinal changes in dietary intake from periconception to pregnancy. Here, we investigated changes in the intake of food and nutrients, and compliance with dietary reference intakes (DRIs) in pregnant women. Methods: The Japan Environment and Children’s Study, a nationwide multicenter prospective cohort study, included 30,373 pregnant women who answered a validated food frequency questionnaire repeatedly to assess changes in dietary intake in periconception and pregnancy. Energy-adjusted intakes of food groups and nutrients were described using the density method. The percentage of women not meeting DRIs was calculated. Results: Of all foods groups examined, intake of food significantly increased from periconception to pregnancy for dairy products (mean difference 23.5 g/1000 kcal, 95% confidence interval [CI] 22.0–25.0 g/1000 kcal), confectionaries (2.0 g/1000 kcal, 1.8–2.2 g/1000 kcal), and soft drinks (1.3 g/1000 kcal, 0.3–2.3 g/1000 kcal). Of all nutrients examined, intake was significantly increased for calcium (mean difference 27 mg/1000 kcal, 95% CI 25–29 mg/1000 kcal), vitamin A (15 μgRE/1000 kcal, 13–18 g/1000 kcal), and saturated fat (0.4% energy, 0.4–0.4% energy). The percentage of women not meeting DRIs increased for vitamin B group, vitamin C, saturated fat and salt. Conclusion: We found that energy-adjusted intakes of calcium, vitamin A, and saturated fat increased from periconception to pregnancy, while intake of other nutrients did not increase. The percentage of women not meeting DRIs increased for water-soluble vitamins, saturated fat, and salt.