Some human-made chemicals can cause problems with the reproductive system, and several studies have looked at whether these chemicals affect how long it takes to get pregnant.

In a literature review recently published in Human Reproduction Update, ECHO researcher Linda Kahn, PhD, MPH, of NYU Langone Health, and her research team compared the results of past studies on human-made chemicals and their impact on pregnancy. The research found a connection between certain chemicals and time to pregnancy, and also identified chemicals that need further research.

To conduct this research, the team reviewed all papers published in English on this topic from January 1, 2007 to August 6, 2019. After searching five science libraries and finding more than 4,500 articles, they narrowed it down to 28 articles with information from 19 studies that took place in North America, Europe, and East Asia.

The review found a strong connection between a chemical group called polychlorinated biphenyls, formerly used in electrical and hydraulic equipment, and longer time to pregnancy. Even though production of these chemicals stopped in the late 1970s, individuals are still exposed to them through soil, water, and building materials. More research needs to be done on brominated flame retardants, found in furniture, clothing, and other household products, and per- and polyfluoroalkyl substances, found in non-stick cookware and stain-resistant fabrics, to determine their impact on time to pregnancy.

“This review is especially important because it shows that certain long-lasting chemicals may increase the time it takes for couples to become pregnant, which can be stressful and lead couples to seek expensive fertility treatment,” Dr. Kahn said. “Although many of the chemicals covered in the review are no longer produced or used in the United States, they can last for years—even decades—in the environment and our bodies, affecting our health.”

The team believes we need more research on newer chemicals that have been invented to replace dangerous ones to figure out exactly how these chemicals interfere with healthy reproduction. For example, there may be certain life stages such as puberty when being exposed to them may be especially damaging.