Background: Recent literature suggest the effect of maternal smoking on risk of hypertensive disorders in pregnancy (HDP) and preeclampsia may differ by ethnicity, however studies on Asians are limited.Methods: We investigated the association between maternal smoking and HDP and preeclampsia, by using a common analysis protocol to analyze the association in six birth cohorts participating in a Japanese consortium of birth cohorts (JBiCC). Results were compared with published results from cohorts not included in this consortium, and where possible produced a meta-analysis including these studies.Results: Meta-analysis of four cohort studies including 28,219 participants produced an odds ratio (OR) of 1.24 (95% confidence interval (CI) 0.88-1.87) for effect of smoking beyond early pregnancy compared to women who did not smoke during pregnancy. These results combined with those from the Japan Environment and Children’s Study (JECS) yielded an OR of 1.19 (95%CI 1.00-1.43, p=0.056). Meta-analysis results for categories of smoking volume were insignificant, but when combined with JECS yielded an OR of 0.86 (95%CI 0.65-1.12) for smoking 1-4 cigarettes, 1.25 (95%CI 0.98-1.60) for smoking 5-9 cigarettes, and 1.27 (95%CI 1.04-1.54) for smoking 10 or more cigarettes per day. All effects were insignificant for preeclampsia.Conclusion: Our results suggest the protective effect of smoking longer, smoking more on HDP and preeclampsia repeatedly observed among Europeans and North Americans likely do not hold for the Japanese.

Background Tracking gestational weight gain (GWG) during pregnancy makes it possible to optimize pregnancy outcomes and GWG growth curves are well suitable for this purpose. The GWG guidelines for Japanese were revised in 2021. However, currently, there are no GWG growth curves to guide women on how to gain weight to meet these guidelines.Methods Using data on 96,631 live births from the Japan Environment and Children's Study (JECS), we created descriptive GWG percentile curves estimated the trajectory of GWG required to meet the GWG guidelines stratified by pre-pregnancy body mass index (BMI) For both analyses, Bayesian mixed models with restricted cubic splines adjusted for maternal characteristics were used.Results GWG curves substantially differed by pre-pregnancy BMI, and were higher among multiparas and those with lower maternal age and with no previous disease. We estimated that underweight, normal weight, overweight and obese women who gain 8.4 to 11.1 kg, 6.4 to 9.1 kg, 3.8 to 6.5 kg, and <1.9 kg at 30 weeks of gestation are on the trajectory to reach the new guidelines at 40 weeks of gestation.Conclusions We provide GWG percentiles curves for Japanese women as well as GWG trajectory curves to meet the new GWG recommendations. These results may help pregnant women monitor weight during their pregnancy.

The COVID-19 pandemic has caused changes in the family food environment, resulting in more families relying on convenience food options. This study aimed to investigate diet quality by convenience food options (namely instant, frozen, and take-out foods) among Japanese school children during the COVID-19 pandemic. We examined the relationship between the frequency of consumption of convenience food options and nutritional status of the school children. The participants (671 children, 10–14 years old) were chosen to form a nationally representative sample of the Japanese population. Using questionnaires completed by the participants’ guardians, information was collected on the frequency of instant, frozen, and take-out food consumption. Habitual food and nutrient intake were collected using a validated food frequency questionnaire, completed by the children with help from their guardian(s). “Frequent” consumption was defined as consumption of instant, frozen, and/or take-out foods on more than 5 days per week. Using 19 nutrients and their respective dietary reference intake (DRI) values, an index was created to label each child’s nutrient intake as “Adequate”, “Inadequate”, “Excess”, or “Deficient.” Compared to children with non-frequent consumption, school children with frequent instant food consumption had significantly higher rates of inadequate nutrient intake (risk ratio (RR) = 3.0 [95% CI: 1.6–5.6]) and excess nutrient intake (RR = 2.3 [95% CI: 1.3–4.2]), while school children with frequent take-out food consumption had significantly higher rates of inadequate nutrient intake (RR = 2.1 [95% CI: 1.3–3.3]). There were no significant differences for children with frequent frozen-food intake. These associations did not change when adjusting for sociodemographic factors. Our results suggest that the frequent consumption of instant or take-out foods among school children results in non-adequate nutritional intake.

Background: The coronavirus disease 2019 pandemic has changed people's lives dramatically. Few data on the acute effects of the pandemic on children's daily lives and well‐being have been published to date. This study aimed to capture its effects on Japanese children during the first peak of the outbreak. Methods: We conducted a web‐based, anonymous cross‐sectional survey targeting Japanese children aged 7–17 years and parents/guardians of children aged 0–17 years. Eligible individuals were invited to participate in the survey from April 30 to May 31, 2020. This self‐report questionnaire examined daily life and behaviors, psychological symptoms, well‐being, quality of life, and positive parenting or abusive behaviors at the very beginning of the outbreak. Results: A total of 2,591 children and 6,116 parents/guardians participated in our survey. Sixty‐two percent of children reported screen time exceeding 2 h. Twenty percent of children reported abusive behaviors by family members. Nine in ten parents/guardians of school‐aged children reported that their child had at least one acute stress symptom in the past month. Average mental health subscale scores from KINDL ^R questionnaire on quality of life were lower than the national average for all grades. Nearly half of parents/guardians refrained from seeking medical care for the child's symptoms. Conclusions: The COVID‐19 pandemic had serious acute impacts on Japanese children's daily lives, well‐being, family relationships, and health‐care utilization, including some impacts that are potentially long‐lasting; thus, proactive interventions and services are needed, as well as longitudinal surveys.

Background: Although prevalence of low birth weight has increased in the last 3 decades in Japan, no studies in Japanese women have investigated whether birth weight is associated with the risk of pregnancy complications, such as pregnancy-induced hypertension (PIH) and gestational diabetes mellitus (GDM).Methods: We used data from the Japan Public Health Center-based Prospective Study for the Next Generation (JPHC-NEXT), a population-based cohort study in Japan that launched in 2011. In the main analysis, we included 46,365 women who had been pregnant at least once, for whom information on birth weight and events during their pregnancy was obtained using a self-administered questionnaire. Women were divided into five categories according to their birth weight, and the relationship between birth weight and risk of PIH and GDM was examined using multilevel logistic regression analyses with place of residence as a random effect.Results: Compared to women born with birth weight of 3,000–3,999 grams, the risk of PIH was significantly higher among women born <1,500 grams (adjusted odd ratio [aOR] 1.60; 95% confidence interval [CI], 1.17–2.21), 1,500–2,499 grams (aOR 1.16; 95% CI, 1.03–1.30), and 2,500–2,999 grams (aOR 1.13; 95% CI, 1.04–1.22). The risk of GDM was significantly higher among women born 1,500–2,499 grams (aOR 1.20; 95% CI, 1.02–1.42), albeit non-significant association among women in other birthweight categories.Conclusions: We observed an increased risk of PIH among women born with lower birth weight albeit non-significant increased risk of GDM among Japanese women.

A fetal growth restriction is related to adverse child outcomes. We investigated risk ratios and population-attributable fractions (PAF) of small-for-gestational-age (SGA) infants in the Japanese population. Among 28,838 infants from five ongoing prospective birth cohort studies under the Japan Birth Cohort Consortium, two-stage individual-participant data meta-analyses were conducted to calculate risk ratios and PAFs for SGA in advanced maternal age, pre-pregnancy underweight, and smoking and alcohol consumption during pregnancy. Risk ratio was calculated using modified Poisson analyses with robust variance and PAF was calculated in each cohort, following common analyses protocols. Then, results from each cohort study were combined by meta-analyses using random-effects models to obtain the overall estimate for the Japanese population. In this meta-analysis, an increased risk (risk ratio, [95% confidence interval of SGA]) was significantly associated with pre-pregnancy underweight (1.72 [1.42–2.09]), gestational weight gain (1.95 [1.61–2.38]), and continued smoking during pregnancy (1.59 [1.01–2.50]). PAF of underweight, inadequate gestational weight gain, and continued smoking during pregnancy was 10.0% [4.6–15.1%], 31.4% [22.1–39.6%], and 3.2% [−4.8–10.5%], respectively. In conclusion, maternal weight status was a major contributor to SGA births in Japan. Improving maternal weight status should be prioritized to prevent fetal growth restriction.