Abstract
As Japan has achieved one of the lowest perinatal mortality rates (PMR), our study aims to estimate trends in and risk factors for perinatal mortality among singleton births in Japan. We used Japanese vital registration data to assess trends in and risk factors for perinatal outcomes between 1979 and 2010. Birth and death registration data were merged. An autoregressive integrated moving average model was fitted separately by sex to the PMR and the proportion of stillbirths. A multilevel Poisson regression model was used to estimate risk factors for perinatal mortality. Between 1979 and 2010 there were 40,833,957 pregnancies and 355,193 perinatal deaths, the PMR decreased from 18.86 per 1,000 all births to 3.25 per 1,000 all births, and the proportion of stillbirths increased from 83.6% to 92.1%. Key risk factors for perinatal mortality were low or high birth weight, prematurity and post maturity, and being from poorer or unemployed families. A higher proportion of excess perinatal deaths could be averted by effective policies to prevent stillbirths and improved research into their interventions and risk factors. As the cost and challenge of maintaining perinatal mortality gains increases, policies need to be targeted towards higher risk groups and social determinants of health.
Highlights
Singletons and births with missing multiplicity data were assessed in this study, as multiple births are known to have different risk factors for perinatal mortality rate (PMR) compared to single births[16]
There was an annual reduction in the PMR of 4.7% for males, and 4.9% for females
Our study found an annual decrease in perinatal mortality and an increasing proportion of stillbirths, suggesting a slower decline in stillbirth rates compared to early neonatal mortality (ENM) rates, as both ENM rates and stillbirth rates are decreasing[23]
Summary
Data on all live births, early neonatal deaths, and stillbirths occurring between 1979 and 2010 were provided by the Ministry of Health, Labour and Welfare (MHLW) in Japan. These data included information such as birth weight, maternal age, gestational age and parity at the municipality level[14,15]. Singletons and births with missing multiplicity data were assessed in this study, as multiple births are known to have different risk factors for PMR compared to single births[16]. Observations with missing prefecture data, gestational age or sex were excluded. Observations were dropped when maternal age was missing, or when there were more than eight previous births or deaths
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