Association Between Periconception Environmental Risk Factors And Spontaneous Abortion Among Reproductive Aged Couples In Rural China

BackgroundPregnant women exposed to environmental risk factors are susceptible to adverse outcomes.It's important to explore the association between environmental risk factors and spontaneous abortion,with goals to reduce the occurrence of adverse pregnancy outcomes and improve reproductive health.Up to the present,environmental tobacco smoking during pregnancy has been proved to be associated with risk of spontaneous abortion,but the association remains unclear with a view of paternal smoking,especially for preconception paternal smoking.Although a few studies with small sample size attempted to identify the association,but preconception paternal smoking was not differentiated from paternal smoking during pregnancy and maternal smoking.Besides,several studies have verified that air pollution and climate change relate to multiple adverse pregnancy outcomes.Air pollution and climate change have become two worldly concerned public health problems.And Although seasonality of spontaneous abortion was observed in variety of areas,no study was identified to assess ambient fine particulate matter and temperature with similar seasonality and its impacts on spontaneous abortion.This thesis aims to comprehensively evaluate preiconception exposure to environmental risk factors and its association with the risk of spontaneous abortion,including husband smoking,environmental fine particulate matter and temperature.MethodsWe conducted a population-based retrospective cohort study among 5 770 691 non-smoking rural Chinese women along with their husbands participated in the National Free Pre-Pregnancy Checkups Project(NFPCP)in 2010-2016.The main outcome was spontaneous abortion(SA).Multivariate logistic regression was used to estimate odds ratios and 95%confident intervals,and restricted cubic spline(RCS)was used to estimate the non-linear relationship.Before excluding participants with maternal smoking or missing such information,we first investigated the association between parental smoking status and SA.We then assessed the association in all included participants.Association between preconception paternal smoking and SA was estimated in participants whose husbands quitted smoking when early-pregnancy follow-up.In addition,the potential protective impact of periconception paternal smoking on SA was also tested.We also conducted a population based retrospective cohort study among 1 190 738 ruralChinese couples participated in NFPCP whose last menstrual period within July 1,2015 and June 30,2016.Daily town-level ambient PM2.5,temperature,relative humidity and surface wind speed were estimated by inverse-distance-weighted method using data from China National Urban Air Quality Real-Time Publishing Platform and China Integrated Meteorological Information Service System.And individual exposure of average PM2.5,accumulated days of PM2.5?75 ?g/m3 for every 10 days,accumulated days of PM2.5?150?g/m3 for every 10 days,average temperature and adjusted temperature using heat index and wind chill index were calculated for two exposure window,including preception(between the 179th day before LMP and LMP)and early-pregnancy(between the day after LMP and the 90th day after LMP).Multivariate logistic regression was used to estimate aOR and 95%CI,and RCS was used to estimate the non-linear response-response relationship.Results1.Compared to neither-smoker couples,the full adjusted aOR of smoking for SA was 1.17(1.16-1.19),1.20(1.00-1.43),and 1.41(1.27-1.57)in the husband-only,wife-only,and mixed group respectively.Compared with participants without paternal smoking,the multivariable-adjusted ORs of paternal smoking for SA were 1.10(1.07-1.13),1.10(1.07-1.12),1.15(1.13-1.17),1.25(1.21-1.30)and 1.33(1.30-1.35)for participants whose husband smoked 1-4,5-9,10-14,15-19,and ?20 cigarettes/day respectively(P linear<0.05;P nonlinear<0.05,almost linearly shaped),and the corresponding aORs of preconception paternal smoking 1.03(0.96-1.11),1.03(0.97-1.08),1.11(1.06-1.16),1.21(1.09-1.33)and 1.23(1.17-1.30)(P linear<0.05;P nonlinear>0.05).In addition,periconception paternal smoking cessation was associated with an 18%(15%-22%)lower risk of SA.2.10?g/m3 increase of PM2.5 in preconception and early pregnancy could increase SA of 11%(9%-13%)and 8%(6%-10%)respectivly;1 day increase of accumulated days of PM2.5?75 ?g/m3 in preconception and early-preganncy could increase SA of 9%(8%-11%)and 7%(6%-8%)respectively;1 day increase of accumulated days of PM2.5?150 ?g/m3 in preconception and early-pregnancy could decease SA of 48%(46%-51%),and 41%(39%-44%)respectively.And the results for different exposure windows and PM2.5 measurement types consisted in subgroup analyses.For couples with at least 1 day of accumulated days of PM2.5?150 ?g/m3 in preconception or early-pregnancy,the OR of SA increased with the increment of PM2.5.For couples with 0 days of accumulated days of PM2.5?150?g/m3 in preconception and early-pregnancy,the OR of SA also revealed a similar trend.3.The aORs(95%CIs)for SA were 1.02(0.99-1.04)and 0.94(0.93-0.96)for 5?increase of ambient temperature in preconception and early-pregnancy,respectively;and the aORs(95%CIs)for SA were 1.03(1.00-1.05)and 0.94(0.93-0.96)for 5 ? increase of ambient adjusted temperature in preconception and early-pregnancy,respectively.And the associations varied among participants with different LMP seasons.For participants with LMP in summer,the aORs(95%CIs)for SA were 1.98(1.87-2.10)and 1.66(1.56-1.76)for 5 ? increase of ambient adjusted temperature in preconception and early-pregnancy,respectively;for participants with LMP in winter,the aORs(95%CIs)for SA were 0.79(0.76-0.82)and 0.78(0.75-0.81)for 5? increase of ambient adjusted temperature in preconception and early-pregnancy,respectively.Subgroup analyses were conducted in different LMP season participants,and the results consisted in subgroups.Conclusions1.Paternal smoking was independently associated with spontaneous abortion.The danger of paternal smoking and the necessity of tobacco control should be emphasized and during preconception and pregnancy counseling.2.Both exposure to PM2.5 in preconception and early-pregnancy could increase the risk of SA,and too high or too low of ambient temperature will also increase the risk of SA.Couples preparing pregnancy or pregnant women should avoid be exposed to highly PM2.5 polluted,high or low temperature enviroments.Effective strategies should be taken to reduce the high level air pollution and greenhouse gas emission.