Association between ambient air pollution and pregnancy outcomes in women undergoing in vitro fertilization
Objective To investigate the association between exposure to ambient air pollutants and pregnancy outcomes in patients undergoing in vitro fertilization(IVF)/intracytoplasmic sperm injection(ICSI),and to clarify the susceptible windows of exposure.Methods A retrospective cohort study was conducted on 2 071 infertile women aged≤40 years who underwent the first fresh cleavage stage embryo transfer in the Department of Reproductive Medicine of the First Affiliated Hospital of Harbin Medical University from January 2014 to December 2021.Patients were divided into heating season group and non-heating season group based on whether the start date of gonadotropin(Gn)was during the heating season or not,and baseline data and pregnancy outcomes were compared between the two groups.Daily average levels of six criteria air pollutants[fine particulate matter(PM2.5),inhalable particulate matter(PM10),nitrogen dioxide(NO2),sulfur dioxide(SO2),carbon monoxide(CO),ozone(O3)max-8 h]in four discrete periods were obtained.The four discrete periods included period 1,75 d prior to Gn start to Gn start;period 2,Gn start to oocyte retrieval;period 3,oocyte retrieval to day 3 embryo transfer;period 4,embryo transfer to serum human chorionic gonadotropin test.The primary outcome was ongoing pregnancy.A multiple logistic regression model was used to investigate the association between air pollutant exposure and pregnancy outcomes,adjusted for important confounders.Results The biochemical pregnancy rate[51.7%(465/900)],the clinical pregnancy rate[45.2%(407/900)],the ongoing pregnancy rate[38.2%(344/900)],and the live birth rate[36.1%(325/900)]in the heating season group were significantly lower than those in the non-heating season group[56.3%(659/1 171),P=0.037;51.2%(599/1 171),P=0.007;44.3%(519/1 171),P=0.005;41.3%(484/1 171),P=0.016].A significant negative correlation was observed between SO2 and NO2 exposure and ongoing pregnancy in all four time windows.SO2 increased by one interquartile range(IQR),corresponding to adjusted OR(a OR)and 95%CI were 0.92(0.85-0.99),0.92(0.87-0.99),0.93(0.87-0.99)and 0.93(0.87-0.99),respectively.An IQR increase in NO2 was also significantly associated with decreased odds of ongoing pregnancy(a OR=0.83,95%CI:0.72-0.95;a OR=0.87,95%CI:0.77-0.97;aOR=0.90,95%CI:0.81-1.00;aOR=0.85,95%CI:0.77-0.95,respectively).During period 1 and period 4,we observed adverse effects of PM10 exposure on ongoing pregnancy(a OR=0.86,95%CI:0.75-0.98;a OR=0.89,95%CI:0.80-1.00,respectively).In Period 1,PM2.5 exposure was significantly associated with reduced odds for ongoing pregnancy with a OR=0.86,95%CI:0.75-0.99.In addition,NO2 exposure was associated with a decreased likelihood of achieving clinical pregnancy across all exposure windows except for period 3.However,no associations were noted with CO and O3.Conclusion Ambient air pollution has detrimental effects on pregnancy outcomes in patients undergoing fresh embryo transfer.Notably,the adverse impacts were also observed during preantral-antral follicle transition stage before IVF/ICSI treatment.A significant negative association between NO2 exposure and pregnancy outcomes was observed in almost all exposure windows,indicating that NO2 may be the main air pollutant associated with adverse pregnancy outcomes.
Fertilization in vitroAmbient air pollutionNO2Ongoing pregnancy
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