Instructor of Medicine
Harvard Medical School
BPA stands for bisphenol A and is a resin used to make water bottles, food package containers, receipts, and more. Similar to phthalates, a product popularly used in cosmetics, BPA has been shown to interfere with ovarian development.
Studies run to understand how bisphenols and phthalates impact fertility have shown little association, but that may be masked by the benefits of products like folic acid and soy. Let’s explain.
When Dutch investigators looked at 900 pregnant women and measured their urinary levels of BPA and phthalate and compared it with how long it took them to conceive, they noticed something interesting: those who took enough folic acid were not delayed by bisphenol or phthalate exposure. However, those not taking enough folic acid experienced the detrimental effects.
Researchers at Harvard did a somewhat similar exercise and looked the issue with IVF patients in mind. The Harvard team tracked 178 fertility patients undergoing over 230 IVF cycles and measured their BPA exposure by concentrations found in their urine. The team then stratified the results by those who consumed high levels of folate (through diet) and low levels.
As you can see below, the group of patients who consumed less folate were negatively affected by greater BPA exposure. Those who consumed more folate witnessed no decline in pregnancy rates after increased BPA exposure.
The same team did a similar analysis based on soy consumption and noticed the same phenomenon: those who consumed soy appeared more protected from the negative effects of greater BPA exposure.
Ultimately, it seems clear that exposure to some environmental toxicants can damage our ability to conceive but that can partially be offset by intake of products like soy, folic acid and other nutrients.
There’s credible reason to believe that exposure to pesticides impairs fertility treatment outcomes. Data published in JAMA by Harvard researchers showed that women who consumed the highest levels of fruits & vegetables exposed to pesticides recorded IVF success rates significantly lower than women who consumed the lowest levels of such foods. And the opposite was true: women who consumed higher levels of low pesticide fruits and vegetables recorded better outcomes.
A similar phenomenon was observed amongst men as it pertains to their semen parameters. As we always note, semen parameters are a “surrogate marker” and not always a reliable stand-in for true success rates.
Ultimately, researchers came to believe major gains could be made when women substituted one daily serving of high pesticide fruits / vegetables for one serving of low pesticide fruits / vegetables. Below we characterize how investigators, and the USDA, classify these fruits and vegetables by their pesticide exposure.
It's become clear that exposure to air pollution likely has a negative on one's ability to conceive and carry.
In Carre's analysis below, multiple studies correlate higher levels of air pollution exposure and longer "time to pregnancy" for "natural conception."
There's emerging evidence that women living in areas with higher levels of air pollution are more likely to see their IVF cycle fail. For instance, investigators at Harvard noted that women who lived in areas with higher levels of nitrogen dioxide (NO2) were over 40% more likely to have their cycle cancelled even before their egg retrieval (presumably on account of discouraging follicular development). This analysis accounts for numerous factors, including socio-economic.
This goes along with a broader body of work published in 2010 on over 7,000 IVF patients. The work showed for every 0.01 particles-per-million a woman was exposed to of Nitrogen Dioxide during all phases of IVF (e.g. between injections and retrieval, between retrieval and transfer, between transfer and live birth), she was roughly 20% less likely to achieve a clinical pregnancy and live birth.