• Associations between air pollution exposure and pregnancy outcomes following In Vitro Fertilization; a review of literature
  • Maryam Malekian,1,* Sara Hasani,2
    1. Tehran University of Medical Sciences
    2. Tehran University of Medical Sciences


  • Introduction: Nowadays air pollution is a global health concern. According to World Health Organization (WHO), almost 99 percent of the global population breathes air that contains a high level of pollutants. Among its multiple adverse impacts reported on human health, we can mention adverse effects on reproductive health and fertility. fifteen percent of reproductive-aged couples are affected by infertility. increasing the number of families with fertility problems, results in more requests for the use of assisted reproduction techniques (ARTs). In vitro fertilization (IVF) is a common form of ART involving the manipulation of oocytes outside the body. In this procedure, the egg is removed from the ovaries and fertilized with sperm in a laboratory, and then returned to the woman's uterine to develop as the embryo. Considering IVF and embryo transfer (ET) have risks and side effects, the success rate, and the pregnancy outcomes are important. Associations between air pollution with various pollutants and adverse pregnancy outcomes have been described by several authors. To summarize the evidence, we will review the association between exposure to air pollutants and pregnancy outcomes following IVF in this article.
  • Methods: A literature search was conducted in electronic databases, and we queried PubMed, Google Scholar, and Science Direct database to identify all relevant studies published before August 2022. Combinations of terms and descriptors related to air pollution, fertility, and In Vitro Fertilization (IVF) technique and MESH search terms were used: air quality, air pollution, air pollutants, in vitro fertilization, fresh embryo transfer and frozen-thawed embryo transfer, pregnancy outcomes, pregnancy rate, live birth. No time or language restrictions were adopted, and queries were limited to human studies. 27 cohort studies were included in this review.
  • Results: pollutants included in these studies were: particulate matter (PM), nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), and ozone (O3). pollutant exposures were studied in different periods of IVF including before oocyte retrieval, the time between oocyte retrieval and embryo transfer, and after embryo transfer. The results showed that air pollutants can significantly affect the IVF pregnancy outcome. For all exposure periods, O3 was positively associated with implantation and live birth. Exposure to PM2.5 and PM10 before oocyte retrieval has an adverse effect on IVF outcomes and showed positive associations with biochemical pregnancy loss. IVF success rates were highest when PM concentrations were lowest and PM10 and CO levels were also inversely associated with intrauterine pregnancy. Likewise, Increased NO2 and SO2 were associated with a lower pregnancy rate and decreased probability of intrauterine pregnancy, however, there was a controversy about whether NO2 significantly modifies reproductive success.
  • Conclusion: metabolites and biologic pathways involved in inflammation and oxidative stress, associated with high exposure to air pollutants, may mediate the lower probability of live birth and increase adverse pregnancy outcomes following ART. Thus, to improve IVF successful outcomes, exposure to air pollutants should be limited, and prospective cohort studies are warranted to investigate the underlying mechanisms accounting for this association.
  • Keywords: air pollution, air pollutants, in vitro fertilization, IVF, pregnancy outcomes