The changing prevalence of infertility.

Infertility is a major, multifaceted issue worldwide whose prevalence is increasing in both high- and low-income countries. The reasons are numerous, and may differ among world regions, but lifestyle and nutritional factors, epidemic infections, and sexually transmitted diseases are major determinants in most latitudes. Three other reasons may explain the increasing incidence of infertility. First, owing to the widespread use of contraception, the choice of delaying the first pregnancy until the third decade of life places men and women at higher risk for sexually transmitted diseases, and women at higher risk for uterine fibroids, endometriosis, polycystic ovary syndrome, and chronic anovulation. Second, prolonged exposure to chronic stress and environmental pollutants may play a critical role in decreasing fertility. Third, gonadotoxic oncologic treatments allow many patients to survive cancer, at the cost of their fertility. This consideration may justify the development of treatments that preserve fertility.