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. 2016;26(2):76-83.
doi: 10.2188/jea.JE20150055. Epub 2015 Dec 5.

Effects of the Great East Japan Earthquake on Secondary Sex Ratio and Perinatal Outcomes

Kohta Suzuki  1 , Zentaro Yamagata, Miyuki Kawado, Shuji Hashimoto
Affiliations

Effects of the Great East Japan Earthquake on Secondary Sex Ratio and Perinatal Outcomes

Kohta Suzuki et al. J Epidemiol. 2016.

Abstract
in English, Japanese

Background: The effect of natural disasters on secondary sex ratio (SSR) and perinatal outcomes has been suggested. This study aimed to examine effects of the Great East Japan Earthquake on perinatal outcomes using vital statistics of Japan.

Methods: Birth registration data from vital statistics of Japan between March 2010 and March 2012 were used. Pregnant women who experienced the earthquake were categorized according to their gestational period as of March 11, 2011, as follows: gestational weeks 4-11, 12-19, 20-27, and 28-36 (2011 group). Similarly, pregnant women who did not experience the earthquake were categorized according to their gestational period as of March 11, 2010 and used as controls (2010 group). We also categorized prefectures as "extremely affected", "moderately affected", and "slightly or unaffected" regions. SSR, birth weight, and gestational period were compared between both groups.

Results: The number of singleton births was 688,479 in the 2010 group and 679,131 in the 2011 group. In the extremely affected region, the SSR among women at 4-11 weeks of gestation was significantly lower in the 2011 group compared with the 2010 group (49.8% vs 52.1%, P = 0.009). In the extremely affected region, children born to women who experienced the earthquake at 28-36 weeks of gestation had significantly lower birth weights.

Conclusions: The SSR declined among women who experienced the earthquake during early pregnancy, particularly in the extremely affected region. However, no apparent negative effect of the earthquake on perinatal outcomes was observed, although birth weight of infants who were born to women who experienced the earthquake at 28-36 weeks of gestation were lower.

背景：: 自然災害が出生性比と周産期予後に影響を与えることが示唆されてきた。本研究では、東日本大震災が周産期予後に与える影響について、人口動態統計を用いて検討することを目的とした。

方法：: 2010年3月から2011年3月までの、人口動態統計出生票データを用いた。東日本大震災を経験した妊婦を、2011年3月11日時点での妊娠週数により妊娠4-11週、12-19週、20-27週、28-36週と分類した（2011年群）。2010年3月11日に妊娠していた女性を同様に分類し、コントロールとして用いた（2010年群）。さらに、都道府県を「深刻な影響を受けた地域」「中程度の影響を受けた地域」「わずかな影響、あるいはほとんど影響はなかった地域」という3群に分類した。出生性比、出生体重、妊娠期間を両群で比較した。

結果：: 2010年群では688,479人、2011年群では679,131人の単胎児が出生した。深刻な影響を受けた地域では妊娠4-11週に分類された妊婦で出生性比が2011年群で2010年群に比べて有意に減少していた（49.8% vs. 52.1%, P = 0.009）。また、深刻な影響を受けた地域では、妊娠28-36週で被災した妊婦は有意に出生体重が小さい児を出産していた。

結論：: 妊娠初期に被災した女性では、特に被害が深刻だった地域で、出生性比が減少していた。しかしながら、震災による周産期予後について、負の影響は明らかにならなかった。

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Figures

Figure.
Figure.. Categorization of prefectures by the extent of damage caused by the earthquake.
See this image and copyright information in PMC

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