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Exploring associations of maternal exposure to ambient temperature with duration of gestation and birth weight: a prospective study

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      Evidence suggests the possible impact of ambient high temperature on fetal growth and birth outcomes. However, little is known about the relative impact of exposure to heat and cold and the possible vulnerable window during pregnancy.


      Data on a total of 237,585 pregnant women from January 1st, 2001 to December 31st, 2010 were acquired from the Queensland Health, Australia. Daily data on meteorological factors, including ambient temperature, relative humidity, barometric pressure, and air pollutants, such as PM 10, SO 2, NO 2, and O 3, were obtained from relevant government agencies. This study was to examine the associations of maternal exposure to ambient temperature (high and low temperatures, in early vs. late pregnancy) with the duration of gestation and birth weight.


      A J-shaped association between minimum temperature at conception and duration of gestation was observed after adjusting for seasonality and other confounders. Compared to women who were exposed to the minimum temperature of 15–20 °C in the first gestational week, exposure to the minimum temperature of > 20 °C significantly increased the duration of gestation by 0.029 weeks (95% CI: 0.008, 0.049). A cumulative effect was found when exposure across the first four weeks was examined. There was an inverted U-shaped relationship between minimum temperature at delivery and the duration of gestation. Compared to women exposed to 15–20 °C, exposure to minimum temperature of > 20 °C and ≤ 10 °C was associated with a shortened gestation by 0.030 weeks (95% CI: -0.052, − 0.008) and 0.018 weeks (95% CI: -0.057, − 0.004), respectively. By contrast, an inverse relationship between maximum temperature and birth weight was observed. Compared to exposure to the maximum temperature of > 30 °C in the last week of pregnancy, maternal exposure to 20–25 °C and < 20 °C significantly increased birth weight by 0.011 kg (95% CI: 0.008, 0.018) and 0.018 kg (95% CI: 0.010, 0.031), respectively. Similarly, a mild cumulative effect was observed when maximum temperature exposure across the four weeks before delivery was evaluated.


      The finding emphasized the importance of keeping an optimal temperature range during pregnancy for reducing the risk of preterm birth and low birthweight.

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      The online version of this article (10.1186/s12884-018-2100-y) contains supplementary material, which is available to authorized users.

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      Most cited references 35

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      Climate change can be expected to have differential effects on different subpopulations. Biological sensitivity, socioeconomic factors, and geography may each contribute to heightened risk for climate-sensitive health outcomes, which include heat stress, air pollution health effects, extreme weather event health effects, water-, food-, and vector-borne illnesses. Particularly vulnerable subpopulations include children, pregnant women, older adults, impoverished populations, people with chronic conditions and mobility and cognitive constraints, outdoor workers, and those in coastal and low-lying riverine zones. For public health planning, it is critical to identify populations that may experience synergistic effects of multiple risk factors for health problems, both related to climate change and to other temporal trends, with specific geographic factors that convey climate-related risks.
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        The influence of season and ambient temperature on birth outcomes: a review of the epidemiological literature.

        Seasonal patterns of birth outcomes, such as low birth weight, preterm birth and stillbirth, have been found around the world. As a result, there has been an increasing interest in evaluating short-term exposure to ambient temperature as a determinant of adverse birth outcomes. This paper reviews the epidemiological evidence on seasonality of birth outcomes and the impact of prenatal exposure to ambient temperature on birth outcomes. We identified 20 studies that investigated seasonality of birth outcomes, and reported statistically significant seasonal patterns. Most of the studies found peaks of preterm birth, stillbirth and low birth weight in winter, summer or both, which indicates the extremes of temperature may be an important determinant of poor birth outcomes. We identified 13 studies that investigated the influence of exposure to ambient temperature on birth weight and preterm birth (none examined stillbirth). The evidence for an adverse effect of high temperatures was stronger for birth weight than for preterm birth. More research is needed to clarify whether high temperatures have a causal effect on fetal health. Copyright © 2011 Elsevier Inc. All rights reserved.
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          High ambient temperature and the risk of preterm delivery.

          With temperatures expected to increase because of climate change, it is essential to study the health outcomes of elevated temperature in vulnerable populations, such as expectant mothers. In this study, the authors estimated the association between heat and humidity, as measured by apparent temperature, and preterm delivery. They conducted a case-crossover analysis of almost 60,000 births spanning 16 counties in California that occurred from 1999 to 2006 between May and September. The authors identified cases of preterm birth from a state registry of births, which were combined with meteorologic and air pollution monitoring data based on residential zip code. High ambient temperature was significantly associated with preterm birth for all mothers, regardless of maternal racial/ethnic group, maternal age, maternal education, or sex of the infant. Results indicated that an 8.6% increase (95% confidence interval: 6.0, 11.3) in preterm delivery was associated with a 10°F (5.6°C) increase in weekly average (lag06) apparent temperature. Greater associations were observed for younger mothers, blacks, and Asians. These associations were independent of air pollutants. Given the significant associations for apparent temperature and preterm delivery found in this study, more large-scale studies of temperature and preterm delivery are warranted.

            Author and article information

            [1 ]ISNI 0000 0004 0368 8293, GRID grid.16821.3c, School of Public Health, , Shanghai Jiao Tong University, ; Shanghai, China
            [2 ]ISNI 0000 0004 0368 8293, GRID grid.16821.3c, MOE - Shanghai Key Laboratory of Children’s Environmental Health, , Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, ; Shanghai, China
            [3 ]ISNI 0000000089150953, GRID grid.1024.7, School of Public Health and Social Work, Institute of Health and Biomedical Innovation (IHBI), , Queensland University of Technology, ; Brisbane, Australia
            +86-21-63846590 ,
            BMC Pregnancy Childbirth
            BMC Pregnancy Childbirth
            BMC Pregnancy and Childbirth
            BioMed Central (London )
            29 December 2018
            29 December 2018
            : 18
            30594173 6311008 2100 10.1186/s12884-018-2100-y
            © The Author(s). 2018

            Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

            Funded by: National Natural Science Foundation of China
            Award ID: 81673183, 81874266
            Award Recipient :
            Funded by: Shanghai public health academic leader project
            Award ID: GWDTR201222
            Award Recipient :
            Funded by: Shanghai Jiao Tong University medicine and engineering cross fund project
            Award ID: YG2013MS13
            Award Recipient :
            Funded by: NHMRC Research Fellowship
            Award ID: 553043
            Award Recipient :
            Funded by: Science and Technology Funds from Pudong New Area, Shanghai
            Award ID: PKJ2017-Y01
            Award Recipient :
            Funded by: Research Funds from Shanghai Jiaotong University School of Medicine
            Award ID: 20170509-1
            Award Recipient :
            Funded by: Scientific Research Development Funds from Xinhua Hospital, Shanghai Jiaotong University School of Medicine
            Award ID: HX0251
            Award Recipient :
            Research Article
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            © The Author(s) 2018

            Obstetrics & Gynecology

            birth weight, duration of gestation, temperature, climate change


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