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There are conflicting findings regarding the association of ozone (O 3) exposure with preterm birth (PTB) occurrence. In the present study, two cohorts were combined to explore the relationship between maternal O 3 exposure during pregnancy and PTB risk, and analyze the underlying mechanisms of this relationship in terms of alterations in the preconception telomere length. Cohort 1 included mothers who participated in the National Free Preconception Health Examination Project in Henan Province from 2014 to 2018 along with their newborns (n = 1,066,696). Cohort 2 comprised mothers who conceived between 2016 and 2018 and their newborns (n = 1871) from six areas in Henan Province. The telomere length was assessed in the peripheral blood of mothers at the preconception stage. Data on air pollutant concentrations were collected from environmental monitoring stations and individual exposures were assessed using an inverse distance-weighted model. O 3 concentrations (100.60 ± 14.13 μg/m3) were lower in Cohort 1 than in Cohort 2 (114.09 ± 15.17 μg/m3). Linear analyses showed that PTB risk decreased with increasing O 3 exposure concentrations in Cohort 1 but increased with increasing O 3 exposure concentrations in Cohort 2. Nonlinear analyses revealed that PTB risk tended to decrease and then increase with increasing O 3 exposure concentrations in both cohorts. Besides, PTB risk was reduced by 88% for each-unit increase in telomere length in those exposed to moderate O 3 concentrations (92.4–123.7 μg/m3, P < 0.05). While no significant association was observed between telomere length and PTB at extreme O 3 concentration exposure during entire pregnancy (<92.4 or >123.7 μg/m3, P > 0.05) in Cohort 2. These findings reveal a nonlinear (U-shaped) relationship between O 3 exposure and PTB risk. Furthermore, telomere with elevated length was associated with decreased risk of PTB only when exposed to moderate concentrations of O 3 , but not when exposed to extreme concentrations of O 3 during pregnancy. [Display omitted] • There was a U-shaped relationship between O 3 exposure and preterm birth (PTB) risk. • In the moderate range, O 3 did not have a positive association with PTB risk. • Telomere length was involved in the U-shaped relationship between O 3 and PTB. • Telomere length was associated with decreased PTB risk for moderate O 3 exposures. [ABSTRACT FROM AUTHOR]

Changes in the preconception ambient temperature (PAT) can affect the gametogenesis, disturbing the development of the embryo, but the health risks of PAT on the developing fetus are still unclear. Here, based on the National Free Preconception Health Examination Project in the rural areas of Henan Province, we evaluate the effects of PAT on preterm birth (PTB). Data of 1,231,715 records from self-reported interviews, preconception physical examination, early gestation follow-up, and postpartum follow-up were collected from 1 January 2013 to 31 December 2016. Generalized additive models were used to assess the cumulative and lag effects of PAT upon PTB. The significant cumulative effects of mean temperature within 2 weeks and 3 weeks on the risk of PTB, especially upon late PTB (34–36 weeks) (P < 0.05), were observed. Exposure to extreme heat (> 90th percentile) within 2 weeks (RR = 1.470) and 3 weeks (RR = 1.375) before conception could increase the risk of PTB. After stratifying PTB, exposure to extreme heat within 2 weeks before conception can increase the risks of early (< 34 weeks) and late PTB (P < 0.05). Besides, exposure to extreme cold (< 10th percentile) within 3 weeks or longer before conception can elevate the risk of PTB, especially late PTB. The significant lag effects of temperature changes on the risk of early PTB (lag-8 days or earlier) were observed. In conclusion, the risk of PTB was susceptible to PAT changes within 2 weeks or longer before conception. Our findings provide (i) guidance for rural couples to make pregnancy plans and (ii) scientific evidence for the government to formulate policies to prevent PTB. [ABSTRACT FROM AUTHOR]

Emerging evidence suggests residential surrounding green space is beneficial for human health. The association between green space and GDM showed inconsistent results, and potential effect modification of green space with air pollution is still unclear. This study aims to evaluate the association between green space and GDM, and further explore potential interaction and medication effects. Participants were recruited from a retrospective cohort study between 2015 and 2020 in Henan, China. Residential green space based on normalized difference vegetation index (NDVI) and air pollution exposure were estimated using spatial-statistical models. Multivariate logistic regression was applied to evaluate the association between per 0.1 unit increase in NDVI with 4 buffer sizes (250 m, 500 m, 1000 m, 2000 m) and GDM. We examined potential interaction of green space and air pollutants on GDM. Mediating effects of air pollution associated with green space exposure on GDM were also investigated by causal mediation analyses. A total of 46,665 eligible pregnant women were identified. There were 4092 (8.8 %) women diagnosed with GDM according to the IADPSG criteria. We found that per 0.1-unit increment in NDVI 250 m , NDVI 500 m , NDVI 1000 m and NDVI 2000 m in second trimester were associated with the decreased risk of GDM, with adjusted OR of 0.921(95 %CI: 0.890–0.953), 0.922 (95 %CI: 0.891–0.953), 0.921 (95 %CI: 0.892–0.952) and 0.921 (95 %CI: 0.892–0.951), respectively. We identified significant interactions between second trimester PM 2.5 and O 3 exposure and NDVI for GDM (P interaction < 0.001). The causal mediation analysis showed that PM 2.5 mediated approximately 2.5–5.5 % of the association between green space and GDM, while the estimated mediating effect of O 3 was approximately 30.1–38.5 %. In conclusion, our study indicates that residential green space was associated with a reduced risk of GDM, particularly second trimester. Green space may benefit to GDM partly mediated by a reduction in PM 2.5 and O 3. [Display omitted] • The association of residential green space with the risk of GDM were explored. • We found second trimester green space were associated with a reduced risk GDM. • Green space may benefit to GDM partly mediated by a reduction in PM 2.5 and O 3. [ABSTRACT FROM AUTHOR]

Air pollution and previous abortion have been reported to be related to preterm birth (PTB). But rare study examined the effect of air pollution on PTB risk among mothers with previous abortion. To estimate the effect of air pollution on PTB and the potential effect modification of previous abortion on such an association in rural part of Henan province (China). Based on National Free Preconception Health Examination Project (NFPHEP), information from the medical records of 57,337 mothers with previous abortion were obtained. An inverse distance-weighted model was used to estimate exposure levels of air pollutants. The effect of air pollution on the risk of PTB was estimated with a multiple logistic regression model. Stratified and interaction analyses were undertaken to explore the potential effect modification of previous abortion on this association. The risk of PTB was positively associated with exposure to levels of nitrogen dioxide (NO 2 ; OR : 1.03; 95% CI : 1.02–1.04)], and sulfur dioxide (SO 2 ; 1.04; 1.02–1.07), and negatively associated with ozone (O 3) exposure (0.97; 0.97–0.98) during the entire pregnancy. Besides, we observed a positive effect of carbon monoxide (CO) exposure during the third trimester of pregnancy on PTB (1.14; 1.01–1.29). The type of previous abortion could modify the effect of air pollution on the PTB risk (P - interaction < 0.05). Compared with mothers with previous induced abortion, mothers with previous spontaneous abortion carried a higher risk of PTB induced by NO 2 , CO, and O 3. The risk of PTB was positively associated with levels of NO 2 , SO 2 and CO, and negatively associated with the O 3 level. The types of previous abortion could modify the effect of air pollution on PTB. Mothers who had an abortion previously, especially spontaneous abortion, should avoid exposure to air pollution to improve their pregnancy outcome. [Display omitted] • The effect of air pollution on PTB among mothers with previous abortion was studied. • The risk of PTB is positively associated with prenatal NO 2 , SO 2 and CO exposure. • Increased O 3 exposure during pregnancy could reduce PTB risk. • Previous abortion type could modify the effect of air pollution on the risk of PTB. • Mothers with previous spontaneous abortion are more sensitive to air pollution. [ABSTRACT FROM AUTHOR]

Due to the poor living and healthcare conditions, preterm birth (PTB) in rural population is a pressing health issue. However, PTB studies in rural population are rare. To explore the effects of air pollutants on PTB in rural population, we collected 697,316 medical records during 2014–2016 based on the National Free Preconception Health Examination Project. Logistic regression models were used to estimate the association between air pollutants and PTB and the modifying effects of demographic characteristics. Relative contribution and principal component analysis-generalized linear model (PCA-GLM) analysis were used to explore the most significant air pollutant and gestational period. Our results demonstrated that PTB risk is positively associated with exposure to air pollutants including PM 10 , PM 2.5 , SO 2 , NO 2 , and CO, while negatively associated with O 3 exposure (P < 0.05). In addition, we found that NO 2 was the largest contributor to the risk of PTB caused by air pollutants (26.5%). The third trimester of pregnancy was the most sensitive exposure window. PCA-GLM analysis showed that the first component (a combination of PM, SO 2 , NO 2 , and CO) increased the risk of PTB. Moreover, we found that rural women who are younger, had higher educated, multi-parity, or smoke appeared to be more sensitive to the association between air pollutants exposure and PTB (P -interaction <0.05). Our findings suggested that increased air pollutants except O 3 were associated with elevated PTB risk, especially among vulnerable mothers. Therefore, the effects of air pollutants exposure on PTB should be mitigated by restricting emission sources of NO 2 and SO 2 in rural population, especially during the third trimester. [Display omitted] • PTB risk was positively associated with prenatal exposure to PM, SO 2 , NO 2 and CO. • Exposure to relatively low concentrations of O 3 can decrease the risk of PTB. • Among pollutants explored, exposure to NO 2 and SO 2 was the major risk factor for PTB. • The third trimester is the most sensitive window for PTB caused by air pollution. • The effect of air pollution on PTB risks varies with an individual's characteristics. [ABSTRACT FROM AUTHOR]

A number of studies have explored the association between ambient temperature and preterm birth (PTB), but rarely among adolescent mothers. To estimate the effects of ambient temperature on the risk of PTB and gestational age of newborns delivered by adolescent mothers in rural areas of Henan province. We obtained 5394 medical records of adolescent mothers with results of pre-pregnancy physical examination and pregnancy outcomes from the National Free Preconception Health Examination Project (NFPHEP) in Henan province. Meteorological information was obtained from the China Meteorological Data Sharing Service System. Individual exposure levels were evaluated with an inverse distance-weighted model. A multiple logistic regression model and multiple linear regression model were used to estimate the effects of ambient temperature on the risk of PTB and gestational age, respectively. Stratified and interaction analyses were also performed. Of newborns in this study, 3.45% (186/5394) were PTB. Mean, maximum and minimum temperature during the entire pregnancy, especially the last 1–4 weeks of pregnancy, were positively associated with the risk of PTB and negatively associated with gestational age (P < 0.05). Nevertheless, a masking effect was observed that gestational age was positively associated with ambient temperature during the first trimester of pregnancy, due to the strongly inverse correlation between ambient temperature during the early and late stages of pregnancy. Stratified analyses showed that increasing temperature during the last 1–4 weeks of pregnancy increased the risk of PTB and decreased gestational age in newborns born in the cold season (P < 0.05). Furthermore, interaction analyses showed that birth season modified the effects of temperature on the gestational age (P interaction < 0.10). Elevated ambient temperature can decrease gestational age and increase the risk of PTB in offspring of adolescent mothers in rural areas. The birth season may modify the effects of temperature on gestational age. [Display omitted] • The vulnerability of offspring of adolescent mothers to temperature was studied. • The risk of PTB is positively related to long- or short-term ambient temperature. • Exposure to higher ambient temperature can decrease the gestational age. • Birth season modifies the effect of temperature on the gestational age. [ABSTRACT FROM AUTHOR]