Analysis of Differences in Preterm Birth Rates According to Household Occupation in Japan From 2007 to 2019

Abstract

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.

Analysis of an Association between Preterm Birth and Parental Educational Level in Japan Using National Data

“…Only one-to-one matching pairs between parents of birth data and couples in the Census were used in the following analyses. As performed in earlier research [4,5], only singleton births were included in the analysis. Additionally, birth records involving parents who were studying at the time were not used.…”

“…Preterm birth rates are known to greatly differ between nations in the world [3], and Japan is recognized to have a comparatively low rate compared to other nations. Although preterm birth rate in Japan has increased since the late 20th century [4], it has remained constant in recent years [5].…”

“…In Japan, some studies investigated socioeconomic factors related to preterm birth. Preterm birth rates are especially high in households without jobs, according to an analysis of national statistics [5]. An epidemiological study of a region in Japan using data from 2002 to 2013 indicated that the relative risk of preterm birth was significantly higher for infants whose father's highest level of education was 13-15 years compared with 10-12 years [9], and an association was not demonstrated for maternal educational level.…”

“…Contrarily, the preterm birth rate has been rather steady in recent years [5], making it important to look into how the rate varies over time depending on educational attainment.…”

Association of maternal nationality with preterm birth and low birth weight rates: analysis of nationwide data in Japan from 2016 to 2020

“…These rates largely vary among countries [3,4] and among the birth place of mothers even within the same country [5,6]. In Japan, the rate of low birth weight or preterm birth is known to vary according to the maternal social characteristics [7][8][9]. However, studies on the association between maternal nationalities and adverse birth outcomes are few in Japan.…”