Does exposure to air pollution during different time windows affect pregnancy outcomes of in vitro fertilization treatment? A systematic review and meta-analysis.

Few researches have examined the impact of air pollution exposure during various time windows on clinical outcomes in women receiving in vitro fertilization (IVF) therapy, and the findings of studies have been conflicting. We investigated the effects of six air pollutants exposure during different time windows (period 1, 85 days before egg retrieval to the beginning of gonadotropin; period 2, the beginning of gonadotropin to egg collection; period 3, egg collection to embryo transfer; period 4, embryo transfer to serum hCG measurement; period 5, serum hCG measurement to transvaginal ultrasonography; period 6, 85 days before egg retrieval to hCG measurement; period 7, 85 days before egg retrieval to transvaginal ultrasonography) on clinical outcomes of IVF therapy. A total of seven databases were searched. NO (period 6), SO (period 2, 3, and 7), CO (period 1, 2 and 7) exposure were linked to lower likelihoods of clinical pregnancy. PM (period 1), PM (period 1), SO (period 1, 2, 3, 4, and 6), NO (period 1) were linked to lower likelihoods of biochemical pregnancy. PM (period 1), SO (period 2 and 4) and CO (period 2) were linked to reduced probabilities of live birth. Our results implied that period 1 might be the most sensitive exposure window. Air pollution exposure is linked to reduced probabilities of clinical pregnancy, biochemical pregnancy, and live birth. Therefore, preventive measures to limit air pollution exposure should be started at least three months in advance of IVF therapy to improve pregnancy outcomes.