Auger Nathalie, Fraser William D, Smargiassi Audrey, Bilodeau-Bertrand Marianne, Kosatsky Tom
Institut national de santé publique du Québec and University of Montreal Hospital Research Centre, Montreal, QC, Canada.
Centre de recherche du CHUS and Department of Obstetrics and Gynecology, University of Sherbrooke, Sherbrooke, QC, Canada.
Int J Epidemiol. 2017 Feb 1;46(1):200-208. doi: 10.1093/ije/dyw077.
The causes of stillbirth are poorly understood, including whether elevated outdoor temperatures increase risk. We assessed the relationship between elevated ambient temperatures and risk of stillbirth by gestational age and cause of death during warm months in a temperate region.
We performed a case-crossover study of 5047 stillbirths in continental Quebec, Canada, between the months of April through September from 1981 to 2011. Using data on maximum daily temperatures adjusted for relative humidity, we estimated associations with stillbirth, comparing temperatures before fetal death with temperatures on adjacent days. The main outcomes were stillbirth according to age of gestation (term, preterm), and cause of death (undetermined, maternal, placenta/cord/membranes, birth asphyxia, congenital anomaly, other).
Elevated outdoor temperatures the week before the death were more strongly associated with risk of term than preterm stillbirth. Odds of term stillbirth for temperature 28 °C the day before death were 1.16 times greater relative to 20 °C (95% confidence interval, CI 1.02-1.33). Elevated outdoor temperature was associated with stillbirth due to undetermined and maternal causes, but not other causes. Compared with 20 °C, the odds of stillbirth at 28 °C were 1.19 times greater for undetermined causes (95% CI 1.02-1.40) and 1.46 times greater for maternal complications (95% CI 1.03-2.07).
Elevated outdoor temperatures may be a risk factor for term stillbirth, including stillbirth due to undetermined causes or maternal complications.
死产的原因尚不清楚，包括室外温度升高是否会增加风险。我们评估了温带地区温暖月份中环境温度升高与孕周及死亡原因导致的死产风险之间的关系。
我们对1981年至2011年4月至9月期间加拿大魁北克大陆地区的5047例死产进行了病例交叉研究。利用根据相对湿度调整后的每日最高气温数据，我们通过比较胎儿死亡前的温度与相邻日期的温度来估计与死产的关联。主要结局是根据孕周（足月、早产）和死亡原因（未确定、母体、胎盘/脐带/胎膜、出生窒息、先天性异常、其他）划分的死产情况。
死亡前一周室外温度升高与足月死产风险的关联比早产死产更强。死亡前一天温度为28°C时的足月死产几率相对于20°C时高出1.16倍（95%置信区间，CI 1.02 - 1.33）。室外温度升高与因未确定和母体原因导致的死产有关，但与其他原因无关。与20°C相比，28°C时因未确定原因导致的死产几率高出1.19倍（95%CI 1.02 - 1.40），因母体并发症导致的死产几率高出1.46倍（95%CI 1.03 - 2.07）。
室外温度升高可能是足月死产的一个风险因素，包括因未确定原因或母体并发症导致的死产。
