272
doi: 10.1111/ppe.12365
Commentary
Temperature and Preeclampsia: Is the Association Valid? Rupa Basu California Environmental Protection Agency, Office of Environmental Hazard Assessment, Oakland, CA
Preeclampsia remains a leading cause of maternal and perinatal morbidity, affecting 3.4% of births in the United States from 1980 to 2010.1 While preeclampsia can be caused by gestational hypertension, many other factors for increased risk remain unknown. Recently, a few investigators have examined the association between temperature and preeclampsia, mostly concluding that preeclampsia risk is increased among conceptions during the warm months and delivery during the cold, often humid months.2 Several mechanisms have been postulated as an explanation, including uterine artery vasoconstriction, leading to decreased uteroplacental blood flow,3 increased blood pressure during periods of exposure to cold temperatures,4 as well as decreased thermal skin conductivity.5 Furthermore, HtrA (high temperature requirement A), a family of serum proteins, have been shown to increase during early onset preeclampsia, and thus, could serve as a potential biomarker.6 In this issue of Paediatric and Perinatal Epidemiology, Auger and colleagues7 assessed the association between temperature and preeclampsia in a large population of 65 273 pregnancies with and 1 825 438 without preeclampsia in Quebec, Canada. Preeclampsia was defined as the onset of hypertension after 20 gestational weeks with proteinuria or end-organ involvement, excluding women who had pre-existing hypertension. Because hospital data were used, an adequate number of cases were available over an extended study period, from 1989 to 2012. Prior to this study, most of the research analysing temperature and preeclampsia were conducted in Australia and Asia, where temperature exposure, biological acclimatisation, population characteristics, health services, and adverse birth outcome rates are different. Quebec offers the unique opportunity to study very cold temperatures as well as some hot temperatures Correspondence: Rupa Basu, California Environmental Protection Agency, Office of Environmental Hazard Assessment, Oakland, CA, USA. E-mail: [email protected]
(mean temperatures typically do not exceed 30°C). The temperature exposure windows considered included 4 weeks after conception and before delivery admission. In agreement with previous literature, preeclampsia prevalence was higher for mean temperatures ≥15.0°C at the start of pregnancy and
doi: 10.1111/ppe.12365
Commentary
Temperature and Preeclampsia: Is the Association Valid? Rupa Basu California Environmental Protection Agency, Office of Environmental Hazard Assessment, Oakland, CA
Preeclampsia remains a leading cause of maternal and perinatal morbidity, affecting 3.4% of births in the United States from 1980 to 2010.1 While preeclampsia can be caused by gestational hypertension, many other factors for increased risk remain unknown. Recently, a few investigators have examined the association between temperature and preeclampsia, mostly concluding that preeclampsia risk is increased among conceptions during the warm months and delivery during the cold, often humid months.2 Several mechanisms have been postulated as an explanation, including uterine artery vasoconstriction, leading to decreased uteroplacental blood flow,3 increased blood pressure during periods of exposure to cold temperatures,4 as well as decreased thermal skin conductivity.5 Furthermore, HtrA (high temperature requirement A), a family of serum proteins, have been shown to increase during early onset preeclampsia, and thus, could serve as a potential biomarker.6 In this issue of Paediatric and Perinatal Epidemiology, Auger and colleagues7 assessed the association between temperature and preeclampsia in a large population of 65 273 pregnancies with and 1 825 438 without preeclampsia in Quebec, Canada. Preeclampsia was defined as the onset of hypertension after 20 gestational weeks with proteinuria or end-organ involvement, excluding women who had pre-existing hypertension. Because hospital data were used, an adequate number of cases were available over an extended study period, from 1989 to 2012. Prior to this study, most of the research analysing temperature and preeclampsia were conducted in Australia and Asia, where temperature exposure, biological acclimatisation, population characteristics, health services, and adverse birth outcome rates are different. Quebec offers the unique opportunity to study very cold temperatures as well as some hot temperatures Correspondence: Rupa Basu, California Environmental Protection Agency, Office of Environmental Hazard Assessment, Oakland, CA, USA. E-mail: [email protected]
(mean temperatures typically do not exceed 30°C). The temperature exposure windows considered included 4 weeks after conception and before delivery admission. In agreement with previous literature, preeclampsia prevalence was higher for mean temperatures ≥15.0°C at the start of pregnancy and
