College of the Environment and Ecology Xiamen University, Xiamen, Fujian, China.
Reproductive Medicine Center, The Affiliated Chenggong Hospital of Xiamen University, Xiamen, Fujian, China.
Hum Reprod. 2019 Mar 1;34(3):441-451. doi: 10.1093/humrep/dey386.
Does outdoor air pollution differentially affect the outcomes of frozen-thawed embryo transfer (FET) and fresh transfer in IVF treatment?
Increased SO2 and O3 levels at the site of IVF unit were significantly associated with lower live birth rates following FET but did not affect the contemporary fresh transfer outcomes.
Ambient air pollution has been associated with human infertility and IVF outcomes. However, most of the studies excluded FET cycles.
STUDY DESIGN, SIZE, DURATION: A retrospective cohort study of 11148 patients contributing to 16290 transfer cycles between January 2013 and December 2016 was carried out.
PARTICIPANTS/MATERIALS, SETTING, METHODS: The average age of the cohort was 31.51 ± 4.48 years and the average BMI was 21.14 ± 2.37 kg/cm2. Inverse distance weighting interpolation was used to estimate the daily ambient exposures to six pollutants (PM2.5, PM10, SO2, NO2, CO, O3) at an IVF clinical site, according to the data from fixed air quality monitoring stations in the city. The exposures of each cycle were presented as average daily concentrations of pollutants from oocyte retrieval to embryo transfer/cryopreservation. Exposures were analyzed in quartiles. A generalized estimating equation was used to evaluate the association between pollutants and IVF outcomes, adjusted for important confounding factors including maternal age, infertility diagnosis, BMI, endometrial status and embryo transfer policy.
The clinical pregnancy rate and live birth rate of the cycles was 55.1% (8981/16290) and 47.1% (7672/16290), respectively. Among the included cycles, 4013 patients received 5299 FET cycles, resulting in 2263 live births (42.7% per ET), whereas 9553 patients received 10991 fresh transfer cycles, resulting in 5409 live births (49.2% per ET). SO2 and O3 levels were significantly associated with live birth rates in FET cycles, whereas none of the pollutants were significantly associated with IVF outcomes in contemporary fresh transfer cycles. The FET cycles in the highest quartile of SO2 and O3 exposure had significantly lower live birth rates (adjusted odds ratio (OR) 0.63, 95%CI 0.53-0.74; 0.69, 95% CI 0.58-0.82, respectively) in comparison with those in the lowest quartile. Models involving all transfer cycles and interaction terms (FET×exposures) suggested that FET significantly enhanced the effects of SO2 and O3 exposure on IVF outcomes (P < 0.001). Multi-pollutant models gave consistent results for the association between SO2 and live birth in FET cycles. Accounting for all six pollutants, women in the highest quartile of SO2 still had the lowest live birth rates (OR 0.61, 95%CI 0.47-0.80).
LIMITATIONS, REASONS FOR CAUTION: The study was limited by its retrospective nature. The exposure data were estimated according to monitoring data rather than measured directly from the IVF unit. Unknown confounding factors may skew the results.
Our data implied that embryos undergoing FET may be more vulnerable to a suboptimal environment than those undergoing fresh transfer. In heavily polluted sites or seasons, fluctuation in FET outcomes may be partially explained by the dynamic changes of ambient gaseous air pollutant.
STUDY FUNDING/COMPETING INTEREST(S): National Natural Science Foundation (81302454). The authors have no conflicts of interest to declare.
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户外空气污染是否会对体外受精（IVF）治疗中的冷冻胚胎移植（FET）和新鲜胚胎移植的结果产生不同影响？
在 IVF 单位现场，SO2 和 O3 水平升高与 FET 后活产率降低显著相关，但不影响同期新鲜胚胎移植的结果。
环境空气污染与人类不育和 IVF 结果有关。然而，大多数研究都排除了 FET 周期。
研究设计、规模、持续时间：对 2013 年 1 月至 2016 年 12 月期间的 11148 名患者 16290 次移植周期进行了回顾性队列研究。
参与者/材料、设置、方法：队列的平均年龄为 31.51 ± 4.48 岁，平均 BMI 为 21.14 ± 2.37kg/cm2。根据城市固定空气质量监测站的数据，采用逆距离加权插值法估算 IVF 临床部位每天的六大气污染物（PM2.5、PM10、SO2、NO2、CO、O3）暴露情况。每个周期的暴露情况表示为从卵母细胞回收到胚胎移植/冷冻保存的污染物的平均日浓度。暴露情况按四分位数进行分析。使用广义估计方程评估污染物与 IVF 结果之间的关联，同时调整了包括母亲年龄、不孕诊断、BMI、子宫内膜状态和胚胎移植政策在内的重要混杂因素。
周期的临床妊娠率和活产率分别为 55.1%（8981/16290）和 47.1%（7672/16290）。在所包括的周期中，4013 名患者接受了 5299 次 FET 周期，导致 2263 次活产（每次 ET 42.7%），而 9553 名患者接受了 10991 次新鲜胚胎移植周期，导致 5409 次活产（每次 ET 49.2%）。SO2 和 O3 水平与 FET 周期的活产率显著相关，而在同期新鲜胚胎移植周期中，没有一种污染物与 IVF 结果显著相关。SO2 和 O3 暴露最高四分位的 FET 周期的活产率明显低于最低四分位（调整后的优势比（OR）0.63，95%CI 0.53-0.74；0.69，95%CI 0.58-0.82）。涉及所有转移周期和交互项（FET×暴露）的模型表明，FET 显著增强了 SO2 和 O3 暴露对 IVF 结果的影响（P<0.001）。多污染物模型为 SO2 与 FET 周期中活产之间的关联提供了一致的结果。在考虑所有六种污染物的情况下，SO2 最高四分位的女性活产率仍然最低（OR 0.61，95%CI 0.47-0.80）。
局限性、谨慎的原因：该研究受到其回顾性性质的限制。暴露数据是根据监测数据估算的，而不是直接从 IVF 单位测量的。未知的混杂因素可能会使结果产生偏差。
我们的数据表明，接受 FET 的胚胎可能比接受新鲜胚胎移植的胚胎更容易受到不利环境的影响。在污染严重的地区或季节，FET 结果的波动可能部分可以通过环境气态空气污染物的动态变化来解释。
研究资金/利益冲突：国家自然科学基金（81302454）。作者没有利益冲突要声明。
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