An American study showed that women who work more than 40 hours per week or are subjected to physical stress, such as difficult exercise and lifting weights, may take longer to get pregnant than other women. Women who work for long periods of time are less able to bear children. This was shown by an American study. According to the study, which was conducted on more than 1,700 female patients in various American states shows that 16% of the women who work more than 40 hours per week failed in their efforts to become pregnant over the course of one year. Meanwhile, 5% of them were able to become pregnant during nearly two years. The women, who were not older than 33, were observed between the years of 2010 and 2014. According to the researchers, a woman's delay in becoming pregnant was directly linked to her work hours. Pregnancy for those who work more than 40 hours was delayed by 20% compared to those who worked between 11 and 40 hours per week. The study also showed that alongside working for more than 40 hours per week, difficult exercise and moving or carrying heavy loads exceeding 10 kilograms on a daily basis and heavy stress also contribute significantly to delaying a woman's ability to bear children.