高温・熱波で早産・死産増える可能性　国際研究

【パリＡＦＰ＝時事】妊娠中の女性が高温や熱波にさらされると、早産や死産の可能性が高くなるとする研究結果が4日、英医学誌ブリティッシュ・メディカル・ジャーナル（BMJ）に発表された。（写真は資料写真）
　こうした妊娠結果は貧困と密接に関連しており、特に熱帯地域でそうだが、地球温暖化に伴い、特に強度と頻度を増す熱波の間にいっそう増える可能性があると研究チームは報告している。
　そして高温への暴露は日常的なことで、しかもエスカレートしているため、たとえわずかな気温の上昇でも公衆衛生上、大きな打撃を与える可能性があると研究は結論付けている。
　今回の研究を行ったのは、南アフリカにある「ウィッツ・リプロダクティブ・ヘルス・ＨＩＶ研究所」のマシュー・チャーシッチ氏が率いる国際チーム。高温が妊娠結果に与える影響を定量化するために、富裕国、貧困国、中所得国、計２７か国の論文７０本を調査した。
　その結果、早産に関する論文４７本のうち４０本が、気温が高いほど早産が多くみられると報告していた。そして早産の確率は気温が１度上昇するごとに平均５％増え、熱波の間は１６％上昇することが新たに判明した。また気温が１度上昇するごとに死産は５％増加し、その相関性は妊娠後期の数週間で最も顕著なことも分かった。
　温暖化によって地球の平均気温は２０世紀の間に１度上昇し、大陸での上昇幅はさらに大きい。国連の「気候変動に関する政府間パネル（ＩＰＣＣ）」は、猛暑日が最も増えるのは熱帯地域だと予想している。
　今回の結果は、暑さに関連する条件が「ハイリスク」になると一般的に考えられているグループに妊娠中の女性が並ぶことを強く示唆するものだと研究チームは結論付けている。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2020/11/04-16:34）

Women exposed to high temperatures and heatwaves during pregnancy are more likely to have premature or stillborn babies, researchers said Wednesday.
Such outcomes -- closely linked to poverty, especially in the tropics -- will likely increase with global warming, especially during more frequent and intense heatwaves, they reported in BMJ, a medical journal.
Even small increases could have a major impact on public health as exposure to high temperatures is common and escalating, the study concluded.
Each year, 15 million babies are born premature, the leading cause of death among children under five, according to the World Health Organization (WHO).
That mortality is concentrated in the developing world, especially Africa.
To quantify the impact of higher heat on pregnancy outcomes, an international team of researchers led by Matthew Chersich from Wits Reproductive Health and HIV Institute in Johannesburg looked at 70 peer-reviewed studies of 27 rich, poor and middle-income nations.
Of the 47 studies that concerned preterm births, 40 reported they were more common at higher temperatures.
The odds of a preterm birth rose, on average, by five percent per one degree Celsius (1C) increase, and by 16 percent during heatwave days, according to the new findings.
Global warming has seen Earth's average temperature rise by 1C over the last century, with greater increases over large land masses.
The number of exceptionally hot days are expected to increase most in the tropics, according to the UN's climate science advisory panel, the IPCC.
- 'High risk' for heat -
Extreme heatwaves -- made more dangerous by high humidity -- are projected to emerge earliest in these regions as well.
Limiting global warming to 1.5C instead of 2C -- goals consistent with the Paris Agreement -- would mean around 420 million fewer people frequently exposed to extreme heatwaves, the IPCC said in a 2018 report.
The new study also found that stillbirths increased by five percent per 1C increase in temperature, with the link most pronounced in the last few weeks of pregnancy.
The impact of warmer days and heatwaves on low birth weight, which is associated with a host of health problems later in life, was smaller, but still significant, the researchers said.
As expected, adverse pregnancy outcomes associated with rising temperatures were strongest among poorer women.
Because other factors such as pollution might play a role in stillbirths and premature babies, the role of warmer temperatures is hard to pin down, the researchers acknowledged.
Nonetheless, the findings are strong enough to suggest that pregnant women merit a place alongside the groups typically considered as at 'high risk' for heat-related conditions, they concluded.
More research and targeted health policies should be a high priority, they added.