A study of 1,286 pregnant women found that those with high levels of per- and polyfluoroalkyl substances (PFAS) in their bodies are 20% more likely to stop breastfeeding early. Published in the Journal of Clinical Endocrinology & Metabolism, research also found that PFAS affect pregnancy outcomes, growth and development into puberty and other aspects of reproductive health. PFAS are synthetic chemicals commonly used in oil- and water-resistant materials.