Among women trying to conceive through in-vitro fertilisation (IVF), those exposed to air pollution have a lower chance of success.
Among women trying to conceive through in-vitro fertilisation (IVF), those exposed to air pollution have a lower chance of success.
Several studies have linked exposure to air pollution during pregnancy to a high risk of preterm delivery and low birth weight. It remains unclear, however, whether poor air quality itself is responsible. To investigate this, researchers followed 7,403 American women who underwent IVF at one of three fertility clinics between 2000 and 2007; the centres were located in rural, urban and suburban areas.
The researchers used data from US Environmental Protection Agency air-quality monitors near each study participant's home and the fertility centres, collected over the seven-year study period.
Of the whole study group, 36 percent of the women had a baby following their first IVF treatment. It was found that these chances dipped by 20 percent when the NO2 levels near a woman's home were 0.01 parts per million above average at the time she was taking medication to spur ovulation. Similar effects were seen when the researchers focused on NO2 levels near the IVF centre at the time of egg retrieval and fertilisation, and levels near the women's homes after the embryos had been implanted. Although IVF labs are tightly controlled environments, their indoor air quality still varies.
One common pollutant - nitrogen dioxide (NO2), largely produced by vehicle exhaust - was consistently linked to lower chances of IVF success. The findings were more complicated when it came to another major pollutant - ozone. Higher-than-average ozone levels after embryo implantation in the womb were associated with lower chances of ultimately having a baby. However, higher ozone exposure around the time of ovulation was connected to improved chances of having a baby.
The reasons for the disparate findings on ozone are not clear. But the positive effects associated with ozone exposure may reflect confounding by NO2 levels. That is, NO2 levels tend to decline as ozone levels rise, and NO2 was the pollutant consistently linked to lesser IVF success in this study.
The findings add to the existing evidence that air quality has subtle effects on human fertility.
Several studies have linked exposure to air pollution during pregnancy to a high risk of preterm delivery and low birth weight. It remains unclear, however, whether poor air quality itself is responsible. To investigate this, researchers followed 7,403 American women who underwent IVF at one of three fertility clinics between 2000 and 2007; the centres were located in rural, urban and suburban areas.
The researchers used data from US Environmental Protection Agency air-quality monitors near each study participant's home and the fertility centres, collected over the seven-year study period.
Of the whole study group, 36 percent of the women had a baby following their first IVF treatment. It was found that these chances dipped by 20 percent when the NO2 levels near a woman's home were 0.01 parts per million above average at the time she was taking medication to spur ovulation. Similar effects were seen when the researchers focused on NO2 levels near the IVF centre at the time of egg retrieval and fertilisation, and levels near the women's homes after the embryos had been implanted. Although IVF labs are tightly controlled environments, their indoor air quality still varies.
One common pollutant - nitrogen dioxide (NO2), largely produced by vehicle exhaust - was consistently linked to lower chances of IVF success. The findings were more complicated when it came to another major pollutant - ozone. Higher-than-average ozone levels after embryo implantation in the womb were associated with lower chances of ultimately having a baby. However, higher ozone exposure around the time of ovulation was connected to improved chances of having a baby.
The reasons for the disparate findings on ozone are not clear. But the positive effects associated with ozone exposure may reflect confounding by NO2 levels. That is, NO2 levels tend to decline as ozone levels rise, and NO2 was the pollutant consistently linked to lesser IVF success in this study.
The findings add to the existing evidence that air quality has subtle effects on human fertility.
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