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.

This study utilized the census data from 2020 and birth data from the vital statistics in 2021 and 2022 in the analysis. Adverse birth outcomes, including preterm birth, term low birth weight (TLBW), and small-for-gestational-age, were examined. Data linkage was conducted between birth data and census data to link parental employment statuses and educational attainments with birth data. Rates of adverse birth outcomes were calculated for each parental employment status. Additionally, regression analysis was used to determine adjusted risk ratios (RRs) of parental employment statuses for each birth outcome.

After data linkage, 334,110 birth records were included in the statistical analysis. Rates for non-regular workers were consistently higher than those for regular workers across all adverse birth outcomes for maternal employment status. Results of regression analyses indicated that the risks of preterm birth for non-regular workers were statistically significantly higher than those for regular workers, both in mothers and fathers with a RR (95% confidence intervals [CIs]) of 1.053 (1.004–1.104) and 1.142 (1.032–1.264), respectively. Furthermore, the risk of TLBW birth for non-regular workers was statistically significantly higher than that for regular workers in fathers (RR [95% CI]: 1.092 [1.043–1.143]).

Our findings demonstrate that non-regular workers have a higher risk of some adverse birth outcomes compared to regular workers.

Work related Musculoskeletal disorders (WMSD) is one of the most important problem in occupational health system of Korea and Japan, where the OHS system developed in similar socio-cultural environment. This study compared WMSD in Korea and Japan to review similarities and differences in their historical background, and development of prevention policies.

Scientific articles, government reports, and related official and non-official statistics on WMSD since the 1960s in Japan and Korea were reviewed.

The historical background and basic structure of the compensation system in Korea and Japan largely overlapped. The issuing of WMSD in both countries appeared as upper limb disorder (ULD), named occupational cervicobrachial diseases (OCD) in Japan, and neck-shoulder-arm syndrome (NSA) 30 years later in Korea, following the change from an industrial structure to automated office work. Both countries developed manuals for diagnosis, guidelines for workplace management, and prevention policies. At present, compensation cases per covered insurers for WMSD are higher in Korea than in Japan, due to the social welfare system and cultural environment. Prevention policies in Korea are enforced more strongly with punitive measures than in Japan. In contrast, the Japanese system requires autonomous effort toward risk control and management, focusing on specific risky processes.

WMSD in Korea and Japan have a similar history of identification and compensation structure, yet different compensation proportions per covered insurer and prevention policies. Follow-up study with international cooperation is necessary to improve both systems.