Correlationan Alysis Of Humidex During Pregnancy With Risk Of Preterm Birth

Significance of The SubjectPreterm birth is the adverse pregnancy outcome that causes the greatest health burden.It not only affects the health and life safety of the mother and fetus,but also is associated with the occurrence and death of diseases in newborns,children and adults.In recent years,numerous studies have confirmed that climate change can have adverse effects on human health,especially on pregnant women and their fetuses.In the studies on the relationship between meteorological factors and the risk of premature birth,most of them are the analysis of the effect of temperature on premature birth,while the evidence of humidity on the risk of premature birth is very limited.However,there is a high degree of collinearity between temperature and humidity.To explore the influence of the combined effect of temperature and relative humidity(humidex)on premature birth,the research results can provide epidemiological evidence for in-depth interpretation of the pathogenesis of premature birth.ObjectivesThe purpose of this study was to explore the association between humidex exposure during pregnancy and the risk of preterm birth,and to explore the key window period for the influence of humidex on the outcome of preterm birth.In addition,the study explored the robustness of the influence of humidex on the outcome of preterm birth according to the research objects of different ages and preterm BMI,providing new ideas for future exploration of the relationship between meteorological factors and preterm birth.MethodsAccording to the purpose of the study,documented maternal data during 2019-2020 were selected from the database.Daily meteorological factors and air pollutant data were collected from cities in Shandong Province during the same period.Individual exposure assessment of temperature and humidity index during pregnancy was performed according to the time of last menstrual cycle and delivery time.At the same time,inverse distance weighting(IDW)was used to estimate individual exposure to air pollutants and other meteorological factors during pregnancy.Then,a generalized additive model(GAM)was established to analyze the correlation between preterm birth and humidex.After controlling confounding factors such as basic demographic characteristics,meteorological indicators and air pollutants,the correlation between preterm birth and humidex was studied.The distribution lag non-linear model(DLNM)combined with logistic regression was used to identify the key window period between the humidex and the risk of premature birth.The age and pre-pregnancy BMI of the subjects were stratified to comprehensively explore the influence of humidex exposure during pregnancy on the risk of premature birth.Sensitivity analysis:DLNM of different exposure matrices were used to assess the robustness of humidex and the risk of preterm birth.Finally,the comfort index range and the attributed risk percentage of non-comfort humidex during pregnancy were obtained.Results1.Incidence of preterm birth:A total of 34,365 subjects were included in this study,among which 1,975 were preterm,with a rate of 5.75%(1975/34365).2.Evaluation results of prenatal humidex exposure:the average exposure value of the whole pregnancy humidex of the subjects was 14.20(-3.63～27.48),and the prenatal humidex of the preterm subjects was significantly higher than that of the normal control population.3.Analysis of the correlation between humidex in pregnancy and the risk of premature birth results:The correlation between humidex and the risk of premature birth was "U" shape;Both low humidex(below 10.22)and high humidex(above 20.99)increased the risk of preterm birth,with OR(95%confidence interval)values of 1.36(95%CI:1.00-1.85)and 1.46(95%CI:1.00-2.13),respectively.4.Sensitive window analysis results:The 37-week exposure matrix based on the DLNM showed that exposure to low humidex P5(6.79)after 24 weeks of pregnancy increased the risk of preterm birth by 1.03(95%CI:1.01-1.06).Exposure to high humidex P95(21.34)after 28 weeks of gestation also increased the risk of preterm birth by 1.02(95%CI:1.00-1.05).The sensitive window period of prenatal humidex exposure on preterm birth was after 28 weeks of gestation.5.The effects of age and BMI were modified:(1)The risk of preterm delivery was higher in women of low age(under 25 years old),and the OR values of exposure to low and high humidex were 1.06(95%CI:1.00-1.12)and 1.08(95%CI:1.00-1.16),respectively.(2)Pre-pregnancy BMI greater than OR equal to 28kg/m2(pre-pregnancy obesity)maternal risk of preterm delivery was lower,low and high humidex exposure OR values were 1.07(95%CI:1.01-1.14)and 1.08(95%CI:1.00-1.16),respectively.6.The suitable humidex during pregnancy ranged from 7.04 to 21.28.The incidence of preterm birth in comfort index range and non-comfort index range were 5.27%and 9.81%,respectively,and the attributable risk percentage was 46.28%.7.Sensitivity analysis results:The 36-week exposure matrix constructed by the DLNM showed that exposure to low humidex P5(6.79)after 26 weeks of gestation and high humidex P95(21.34)after 25 weeks of gestation both increased the risk of preterm delivery,with OR values of 1.02(95%CI:1.00-1.05)and 1.02(95%CI:1.00-1.04).Conclusions1.The humidex,which reflects the comprehensive effect of ambient temperature and humidity,is associated with the risk of premature birth,and the relationship between the humidex and the risk of premature birth is non-linear.Too low or too high environmental humidex will increase risk of preterm birth.2.Late pregnancy is low or high humidex key exposure to the early effect window.3.Pregnant women of younger age were more likely to be affected by the adverse environmental humidex,pregnant women who were obese before pregnancy were less likely to be affected by the adverse environmental humidex.4.The appropriate humidex during pregnancy ranged from 7.04 to 21.28,and the AR%of uncomfortable humidex during pregnancy was 46.28%.