As few studies have explored the association between non-regular or precarious employment in parents and adverse birth outcomes, this study aimed to investigate this association using national data in Japan.

As few studies have explored the association between non-regular or precarious employment in parents and adverse birth outcomes, this study aimed to investigate this association using national data in Japan.

As few studies have explored the association between non-regular or precarious employment in parents and adverse birth outcomes, this study aimed to investigate this association using national data in Japan.

Objectives: No studies have examined the association between preterm birth rates and socioeconomic factors in Japan using nationwide statistical data. We analyzed the association between preterm birth rates and household occupation using Vital Statistics data. Methods: Aggregated Vital Statistics data from Japan from 2007 to 2019 were obtained from the Ministry of Health, Labour and Welfare. From the data, the number of births according to year, age group, gestational period, number of pregnancies, and household occupation were used in this study. Crude preterm birth rates and preterm birth rates adjusted by maternal age according to household occupation were calculated for each year. Poisson regression analysis was conducted to evaluate the association between household occupation and preterm births. Results: Unemployed households had the highest preterm birth rate, and households with an occupation classification of “full-time worker 2” (an employee at a large company, civil servant, or board member) had the lowest preterm birth rate throughout each period. Poisson regression analysis revealed that unemployed households were statistically significantly associated with a high preterm birth risk. In contrast, the preterm birth rate adjusted by maternal age remained stable throughout each period regardless of household occupation, and preterm birth rates were found not to have increased in recent years in Japan. Conclusions Unemployed households had higher preterm birth rates than other household occupations. Further studies investigating the characteristics of unemployed households are needed to identify the reasons for this disparity.

Objectives: Prior research has not yet examined the relationship between post-term birth and neonatal mortality in Japan, along with factors associated with post-term birth. We investigated these associations utilizing nationwide birth data from Japan. Methods: Birth and mortality data were obtained from the Vital Statistics of Japan for the years 2017 to 2022. The post-term birth rate was calculated by birth characteristics, and the neonatal mortality rates for post-term and term births were computed. Additionally, log-binomial regression analysis was employed to explore the associations between post-term birth and neonatal mortality, as well as between various characteristics and post-term birth. The characteristics considered included infant sex, maternal age group, parity, maternal nationality, maternal marital status, and household occupation. Results: This study analyzed data from 4 698 905 singleton infants born at 37 weeks of gestational age or later. Regression analysis revealed that post-term birth was positively associated with neonatal mortality. The adjusted risk ratio for neonatal mortality in post-term compared to term births was 8.07 (95% confidence interval, 5.06 to 12.86). Factors positively associated with post-term birth included female infant sex, older maternal age, primiparity, non-Japanese maternal nationality, unmarried status, and various household occupations, including farmer, full-time worker at a smaller company, other type of worker, and unemployed. Younger maternal age was inversely associated with post-term birth. Conclusions In Japan, post-term birth represents a risk factor for neonatal mortality. Additionally, socio-demographic characteristics, such as maternal marital status, nationality, and parity were found to be predictors of post-term birth.

Objectives: Prior research has not yet examined the relationship between post-term birth and neonatal mortality in Japan, along with factors associated with post-term birth. We investigated these associations utilizing nationwide birth data from Japan. Methods: Birth and mortality data were obtained from the Vital Statistics of Japan for the years 2017 to 2022. The post-term birth rate was calculated by birth characteristics, and the neonatal mortality rates for post-term and term births were computed. Additionally, log-binomial regression analysis was employed to explore the associations between post-term birth and neonatal mortality, as well as between various characteristics and post-term birth. The characteristics considered included infant sex, maternal age group, parity, maternal nationality, maternal marital status, and household occupation. Results: This study analyzed data from 4 698 905 singleton infants born at 37 weeks of gestational age or later. Regression analysis revealed that post-term birth was positively associated with neonatal mortality. The adjusted risk ratio for neonatal mortality in post-term compared to term births was 8.07 (95% confidence interval, 5.06 to 12.86). Factors positively associated with post-term birth included female infant sex, older maternal age, primiparity, non-Japanese maternal nationality, unmarried status, and various household occupations, including farmer, full-time worker at a smaller company, other type of worker, and unemployed. Younger maternal age was inversely associated with post-term birth. Conclusions In Japan, post-term birth represents a risk factor for neonatal mortality. Additionally, socio-demographic characteristics, such as maternal marital status, nationality, and parity were found to be predictors of post-term birth.

Objectives: Prior research has not yet examined the relationship between post-term birth and neonatal mortality in Japan, along with factors associated with post-term birth. We investigated these associations utilizing nationwide birth data from Japan. Methods: Birth and mortality data were obtained from the Vital Statistics of Japan for the years 2017 to 2022. The post-term birth rate was calculated by birth characteristics, and the neonatal mortality rates for post-term and term births were computed. Additionally, log-binomial regression analysis was employed to explore the associations between post-term birth and neonatal mortality, as well as between various characteristics and post-term birth. The characteristics considered included infant sex, maternal age group, parity, maternal nationality, maternal marital status, and household occupation. Results: This study analyzed data from 4 698 905 singleton infants born at 37 weeks of gestational age or later. Regression analysis revealed that post-term birth was positively associated with neonatal mortality. The adjusted risk ratio for neonatal mortality in post-term compared to term births was 8.07 (95% confidence interval, 5.06 to 12.86). Factors positively associated with post-term birth included female infant sex, older maternal age, primiparity, non-Japanese maternal nationality, unmarried status, and various household occupations, including farmer, full-time worker at a smaller company, other type of worker, and unemployed. Younger maternal age was inversely associated with post-term birth. Conclusions In Japan, post-term birth represents a risk factor for neonatal mortality. Additionally, socio-demographic characteristics, such as maternal marital status, nationality, and parity were found to be predictors of post-term birth.