Effects of the Great East Japan Earthquake on perinatal outcomes
Methods: Birth registration data from vital statistics of Japan between March 2010 and March 2012 were used for analysis. Pregnant women were categorized according to their gestational period as of March 11, 2011, as follows: gestational months 2–3, 4–5, 6–7, and 8–9 (2011 group, n=679,131). Similarly, pregnant women categorized according to their gestational period as of March 11, 2010 were used as controls (2010 group, n=688,479). Moreover, we categorized prefectures as “extremely affected” (Iwate, Miyagi, and Fukushima), “moderately affected,” and “slightly or unaffected” regions. Secondary sex ratio, birth weight, and gestational period were compared between both groups in each category and region.
Results: In the extremely affected region, male-to-female ratio among the women in their 2–3 months of gestation significantly declined in the 2011 group compared with the 2010 group (49.8% vs. 52.1%, p=0.006). In the same region, the gestational periods among the women in their 2–3 months of gestation were significantly shorter in the 2011 group than in the 2010 group (274.6 days vs. 275.1 days, p=0.02). Moreover, these effects were especially greater in the Iwate prefecture than in the other 2 prefectures. However, the differences between the 2010 and 2011 groups were not significant in other regions.
Conclusion: This is the first study to analyze the effects of the Great East Japan Earthquake on perinatal outcomes giving consideration to seasonal patterns of perinatal indicators, and suggests that these effects might be observed only in extremely affected areas.