Birth and pregnancy numbers decreased during the COVID-19 pandemic in Japan: A time series analysis with the ARIMA model

Aim

The long-term effects of the COVID-19 pandemic on birth and pregnancy trends in Japan remain unclear. Although major sporting events are usually followed by an increase in births 9 months later, Japan's fifth wave of COVID-19 occurred during the Olympics held in Japan during the summer of 2021. In this study, we analyzed how the number of births and pregnancies changed during the COVID-19 pandemic and large-scale events in Japan.

Methods

We utilized monthly vital statistical data from birth certificates spanning the years 2010 to 2022. Our analysis followed the identification, estimation, and forecasting stages of autoregressive integrated moving average (ARIMA) modeling. We found the ARIMA (1, 12, 12) model to be adequate for forecasting the monthly number of births.

Results

Comparing actual birth data from 2020 to 2022 with our forecast, we observed a significant decrease in births across all of Japan, urban residential areas, and 13 prefectures—primarily metropolitan regions—in January 2021 and May 2022. We also observed a decrease in pregnancy notifications in May 2020, May 2021, and October 2021. The decrease in births in May 2022 in Japan aligns with the decrease in pregnancy notifications 8 months earlier in October 2021.

Conclusions

Although major sporting events are expected to lead to an increase in the number of births approximately 9 months later, the number of births decreased in May 2022 during the fifth wave of the COVID-19 pandemic in Japan. These findings suggest that the number of pregnancies and births should be monitored in future pandemics with particular attention to fertility trends.