Zhang Yunquan, Yu Chuanhua, Wang Lu
Department of Epidemiology and Biostatistics, School of Health Sciences, Wuhan University, 185 Donghu Road, Wuchang District, Wuhan 430071, China.
Department of Epidemiology and Biostatistics, School of Health Sciences, Wuhan University, 185 Donghu Road, Wuchang District, Wuhan 430071, China; Global Health Institute, Wuhan University, 8 Donghunan Road, Wuchang District, Wuhan 430072, China.
Environ Pollut. 2017 Jun;225:700-712. doi: 10.1016/j.envpol.2017.02.066. Epub 2017 Mar 9.
Seasonal patterns of birth outcomes have been observed worldwide, and there was increasing evidence that ambient temperature played as a trigger of adverse birth outcomes, such as preterm birth (PTB), low birth weight (LBW), and stillbirth. To systematically review updated epidemiological evidence about the relationship between temperature exposure during pregnancy and PTB, LBW, and stillbirth, we searched for related studies published in English from electronic databases and references of identified papers. We only included original articles that directly reported the effects of prenatal temperature exposure on birth outcomes. The characteristics and main findings of included studies were examined. A total of 36 epidemiological studies were finally included in this review. Most of these studies focused on PTB and LBW, while less attention has been paid to stillbirth that was relatively rare in the occurrence. Several designs including ecological (e.g., descriptive and time-series) and retrospective cohort studies (e.g., case-crossover and time-to-event) were applied to assess temperature effects on birth outcomes. Temperature metrics and exposure windows varied greatly in these investigations. Exposure to high temperature was generally found to be associated with PTB, LBW, and stillbirth, while several studies also reported the adverse impact of low temperature on birth outcomes of PTB and LBW. Despite no conclusive causality demonstrated, the current evidence for adverse effect on birth outcomes was stronger for heat than for cold. In summary, the evidence linking birth outcomes with ambient temperature was still very limited. Consequently, more related studies are needed worldwide and should be conducted in diversified climate zones, so as to further ascertain the association between temperature and birth outcomes. Future studies should focus on more sophisticated study designs, more accurate estimation of temperature exposure during pregnancy, and more efficient methods to find out the exposure windows, as well as cold-related effects on birth outcomes.
全球范围内均观察到了出生结局的季节性模式，并且越来越多的证据表明环境温度是早产、低出生体重和死产等不良出生结局的触发因素。为了系统回顾有关孕期温度暴露与早产、低出生体重和死产之间关系的最新流行病学证据，我们从电子数据库以及已识别论文的参考文献中搜索了英文发表的相关研究。我们仅纳入直接报告产前温度暴露对出生结局影响的原创文章。对纳入研究的特征和主要发现进行了审查。本综述最终共纳入36项流行病学研究。这些研究大多聚焦于早产和低出生体重，而对于发生率相对较低的死产关注较少。几种设计，包括生态学研究（如描述性和时间序列研究）以及回顾性队列研究（如病例交叉研究和事件时间研究）被用于评估温度对出生结局的影响。在这些调查中，温度指标和暴露窗口差异很大。一般发现高温暴露与早产、低出生体重和死产有关，而一些研究也报告了低温对早产和低出生体重出生结局的不利影响。尽管尚未证明存在确凿的因果关系，但目前关于高温对出生结局产生不良影响的证据比低温更强。总之，将出生结局与环境温度联系起来的证据仍然非常有限。因此，全球需要更多相关研究，并且应在不同气候区开展，以便进一步确定温度与出生结局之间的关联。未来的研究应侧重于更精密的研究设计、更准确地估计孕期温度暴露以及更有效的方法来确定暴露窗口，以及低温对出生结局的影响。
