Impact of the Great East Japan Earthquake on spontaneous abortion and induced abortion: A population-based cross-sectional and longitudinal study in the Fukushima Prefecture based on the census survey of the Fukushima maternity care facility and vital statistics

Aim: The 2011 Great East Japan Earthquake (GEJE) was a disaster leading to radiation exposure and psychological distress, particularly among pregnant women. However, it is not known how this affected the seasonal changes of pregnancy and childbirth. Therefore, this study investigated the impact of the GEJE in the Fukushima Prefecture on spontaneous and induced abortions with regard to seasonal variability.Methods: We used the data of vital statistics of live birth and stillbirth registry and the census survey of the Fukushima Maternity Care Facility. We calculated the spontaneous and induced abortion rate for 2011-2016 using two different methods (cross-sectional and longitudinal). We calculated the quartiles and outliers to determine the impact and duration of the GEJE. Periodicity was investigated using spectral density analysis. The data were analyzed for the entire Fukushima Prefecture and by region.Results: The spontaneous abortion rate did not show specific changes after the GEJE. Contrarily, the monthly analysis in the cross-sectional method, revealed specific increases in induced abortion rate during the year after the GEJE; in the longitudinal method, induced abortions increased among women who became pregnant within 1 year after the GEJE. Spontaneous abortion showed no specific periodicity, while induced abortion showed cycles of 6 and 12 months, with a particular increase in May each year.Conclusions: The spontaneous abortion rate was not affected by the GEJE. The changes in the induced abortion rate after the disaster may have overlapped with the timing of the increased periodicity, and cannot be attributed solely to the GEJE.