Clinical and Translational Research Center, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, 201204 Shanghai, China.
Centre for Assisted Reproduction, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, China.
Environ Int. 2021 Mar;148:106377. doi: 10.1016/j.envint.2021.106377. Epub 2021 Jan 19.
The effects of ambient air pollutants on adverse pregnancy outcomes have been reported. However, studies about air pollutants exposure and pregnancy outcomes in patients undergoing IVF were limited and inconclusive. To date Shanghai has been the only city in China to implement a compulsory single embryo transfer policy for all patients undergoing their first embryo transfer procedure effective from January 2019. We aimed to investigate the associations between exposure to ambient air pollutants and biochemical pregnancy and live births, and to identify potential vulnerability characteristics of patients undergoing IVF in Shanghai, China.
A retrospective cohort study was conducted on 2766 infertile patients aged ≤ 45 years who underwent first fresh or frozen-thawed cleavage stage embryo transfer in the Shanghai First Maternity and Infant Hospital during April 2016 and December 2019. Daily average ambient levels of six air pollutants (PM, PM, NO, SO, CO and O max-8h) were obtained from fixed air monitors located in closest proximity to patients' residences. The cumulative average level was calculated during three different exposure periods (period1: three months before oocyte retrieval to serum hCG test; period 2: from serum hCG test to live birth outcome; period 3: from three months before oocyte retrieval to live birth). Multiple logistic regression model was performed to investigate associations between exposure to ambient air pollutants and pregnancy outcomes. Stratified analyses were conducted to explore the potential effects modifier.
The biochemical pregnancy rate and live birth rate were 54.2% and 36.4%, respectively. The ambient NO exposure was significantly associated with a 14% lower pregnancy rate during period 1 (aOR = 0.86, 95%CI: 0.75-0.99). The ambient PM was related to significantly increased risk of lowering live birth rate among the patients during period 3 [aOR = 0.88(0.79-0.99)]. Stratified analysis showed that ambient PM was also significantly associated with a reduced pregnancy rate (aOR = 0.82, 95% CI: 0.69-0.97) in patients who underwent single embryo transfer during period 1. Subjects who underwent single embryo transfer also had a decreased likelihood of a live birth when exposed to ambient SO and O during period 3 [aOR = 0.74(0.57-0.95), and 0.92 (0.83-0.98), respectively]. Moreover, O exposure was associated with decreased live birth rates in patients living in non-urban areas. Sensitivity analyses indicated robust negative association between PM exposure and live birth outcomes.
Our study suggested that exposure to ambient air pollutants, in particular NO and PM, was associated with an increased risk of lower rates of pregnancy and live birth respectively in patients undergoing IVF. Stratified analyses indicated that ambient SO and O levels were related to adverse pregnancy outcomes in some subgroups of IVF patients in this study. Notably, patients who underwent single embryo transfer were more susceptible to ambient air pollution exposure. Thus, prospective cohort studies are needed to investigate the underlying mechanisms and the susceptibility windows for women undergoing IVF treatment.
已有研究报告称，环境空气污染物会对不良妊娠结局产生影响。然而，有关接受体外受精（IVF）的患者暴露于空气污染物与妊娠结局的研究有限且尚无定论。截至目前，中国上海是唯一一个从 2019 年 1 月起对所有首次胚胎移植患者实施强制性单胚胎移植政策的城市。我们旨在调查环境空气污染物暴露与生化妊娠和活产之间的关联，并确定中国上海接受 IVF 的患者潜在的脆弱特征。
这是一项回顾性队列研究，纳入了 2016 年 4 月至 2019 年 12 月期间在上海第一妇婴保健院接受首次新鲜或冷冻解冻卵裂期胚胎移植、年龄≤45 岁的 2766 名不孕患者。从距离患者住所最近的固定空气监测站获得了六种空气污染物（PM 、PM 、NO、SO 、CO 和 O max-8h）的每日平均环境水平。在三个不同的暴露期（期 1：从卵母细胞采集前三个月到血清 hCG 检测；期 2：从血清 hCG 检测到活产结局；期 3：从卵母细胞采集前三个月到活产）计算累积平均水平。采用多因素逻辑回归模型来探讨暴露于环境空气污染物与妊娠结局之间的关联。进行分层分析以探索潜在的效应修饰因素。
生化妊娠率和活产率分别为 54.2%和 36.4%。NO 环境暴露与期 1 妊娠率降低 14%显著相关（比值比[OR] = 0.86，95%置信区间[CI]：0.75-0.99）。PM 与患者期 3活产率显著降低相关（OR = 0.88（0.79-0.99））。分层分析显示，PM 还与期 1 单胚胎移植患者的妊娠率降低显著相关（OR = 0.82，95%CI：0.69-0.97）。在期 3，SO 和 O 环境暴露与单胚胎移植患者的活产率降低显著相关[OR = 0.74（0.57-0.95）和 0.92（0.83-0.98）]。此外，O 环境暴露与非城市地区患者的活产率降低相关。敏感性分析表明，PM 暴露与活产结局呈负相关。
本研究表明，接受体外受精的患者暴露于环境空气污染物，尤其是 NO 和 PM ，与妊娠率和活产率降低的风险增加分别相关。分层分析表明，本研究中某些亚组的 IVF 患者的 SO 和 O 水平与不良妊娠结局有关。值得注意的是，接受单胚胎移植的患者更容易受到环境空气污染的影响。因此，需要进行前瞻性队列研究以探讨女性接受 IVF 治疗的潜在机制和易感窗口期。
