Association Between Environmental Temperature During Pregnancy And The Risk Of Gestational Diabetes Mellitus

BackgroundWith global warming,frequent extreme weather and climate variability,more and more studies focus on the impact of environmental temperature on human health.Women’s thermoregulation ability decreases during pregnancy,and they are vulnerable to ambient temperature rise and heat wave.Therefore,pregnant women,as a vulnerable group susceptible to extreme temperature,should be paid more attention.As a common metabolic disease during pregnancy,gestational diabetes mellitus(GDM)not only causes a variety of adverse pregnancy outcomes such as premature delivery,macrosomia,larger than gestational age,but also causes long-term health impacts on pregnant women and their offspring.In recent years,with the continuous improvement of living standards,the incidence of GDM is increasing in China,and the prevention of GDM can reduce the huge disease burden.Studies have shown that the environment temperature and significantly associated with an increased risk of GDM.However,previous studies were limited to exploring the shortterm effect of temperature.As a metabolic disease with long-term development,it is far from enough to analyze the influence of temperature exposure on GDM in a period or a certain point of time before diagnosis.It is necessary to further explore the key exposure window of temperature during pregnancy affecting the risk of GDM in different regions.ObjectivesThis study aims to explore the effect of ambient temperature during pregnancy on the risk of GDM and identify the association and key exposure window between ambient temperature during pregnancy and the risk of GDM,in order to provide evidence from temperate monsoon climate regions for studying the association between ambient temperature and the risk of GDM.The results of this study provide a scientific basis for understanding the pathogenesis of GDM,controlling the occurrence of GDM and formulating corresponding preventive measures.MethodsBased on the Shandong multi-center medical big data platform,this study selected pregnant women with delivery records in Jinan City from 2018 to 2020 as the target population.GDM was hospital-diagnosed,and the relevant information was obtained from the obstetric hospital delivery record and the first prenatal care record.Environmental temperature indicators including the daily highest temperature(Tmax),the daily minimum temperature(Tmin),the mean daily temperature(Tmean),the relevant data from the environmental information monitoring center in Shandong province.The diurnal temperature range(DTR)was defined as the difference between the daily maximum temperature and the daily minimum temperature,and the daily exposure level was calculated according to the time of the last menstrual period.Using the generalized additive model(generalized additive model,GAM)and logistic regression analysis between ambient temperature and GDM risk during pregnancy.A GAM was used to construct the binary response surface of temperature and humidity to visualize the interaction.Multiplicative and additive interaction indicators were calculated to analyze the interaction between temperature exposure during pregnancy and BMI or age.distribution lag nonlinear models(DLNMs)were used to analyze the key exposure Windows of temperature on the risk of GDM.The 99th percentile(P99)of each temperature variable(Tmax,Tmin,Tmean)was defined as extremely high value,and the 1st percentile(P1)was defined as extremely low value.DLNMs was also used to calculate the effect of each IQR increase in DTR.All statistical analyses were performed based on R 4.0.5,two-sided test,P value<Results of 0.05 were considered statistically significant.Results1.Incidence of GDM A total of 3052 pregnant women who met the inclusion criteria were included in this study(382 GDM and 2607 non-GDM).The incidence of GDM in pregnant women who underwent OGTT at 24-28 weeks of gestation was 12.52%.2.Descriptive analysis of ambient temperature and humidity during pregnancy The median temperature(IQR)was 18.01(17.17)in the first trimester and 14.05(18.69)in the second trimester.There were significant differences in the distribution of weekly mean values of meteorological variables between GDM and non-GDM groups(P<0.05).GDM group was characterized by higher mean temperature,larger mean diurnal temperature range and lower mean relative humidity.3.Effects of mean temperature during pregnancy on the risk of GDM The association between temperature in the second trimester and the risk of GDM was statistically significant(P<0.001).Temperature between 12.04℃ and 17.96℃ can reduce the risk of GDM,and temperature above 25.18℃ can increase the risk of GDM.Logistic regression analysis showed that high temperature(>25.18℃)were risk factors for GDM,and the adjusted OR(95%CI)was 1.67(1.15-2.45).After stratified by the warm(May to October)and cold(November to April)seasons of pregnancy,the effect of ambient temperature was statistically significant only in the second trimester of pregnancy in the cold season(P<0.001)The temperature between 13.75℃ and 20.92℃ can reduce the risk of GDM,and the temperature higher than 26.50℃ can increase the risk of GDM.4.Interaction analysis of environmental temperature and other factors on GDM during pregnancy There was a statistically significant interaction between temperature and humidity during pregnancy in the incidence of GDM(X2=14.78,P<0.001).The risk of GDM was greatest under high temperature and low humidity.The multiplicative interaction terms and additive interaction indicators of temperature with age and BMI in the second trimester were not statistically significant(P>0.05).5.Critical exposure window The critical exposure window for the effect of extreme high temperature on GDM was between 13 and 18 weeks of pregnancy,and the OR value of the effect of extreme high temperature on the risk of GDM was the largest at 16 weeks of pregnancy.The risk of GDM increased for each IQR(2.2 ℃)increase in DTR between 17 and 21w of gestation.Conclusions1.Ambient temperature during pregnancy is associated with the risk of GDM,and exposure to higher ambient temperature during pregnancy increases the risk of GDM;2.Cold season(November to April the following year),pregnant women,the effect is more obvious;3.The mid pregnancy is the key to the environment temperature influence the GDM risk period,including at 13 to 18 w is the key to the extreme heat exposure window,17 to 21 w is the key to the DTR exposed window;4.The temperature and humidity on the pathogenesis of GDM pregnancy risk existing in the statistical sense of the interaction,in high temperature and low humidity environment;the highest risk of GDM.Recommend that pregnant women in the 2nd trimester should avoid exposure to extreme high temperatures and temperature changes in the larger environment.