Exercise and weight loss improves ovulation in women who have polycystic ovary syndrome (PCOS), a common hormone disorder that often causes infertility, a new study says.

"The findings confirm what we have long suspected - that exercise and a healthy diet can improve fertility in women who have PCOS," said one of the study authors, Richard Legro, a professor at Penn State College of Medicine in Pennsylvania.

Polycystic ovary syndrome is the most common cause of female infertility. The condition occurs when a woman's body produces slightly higher than normal amounts of testosterone and other androgens, sex hormones associated with male traits.

The resulting hormone imbalance can cause irregular or absent menstrual periods, weight gain, acne, excess hair on the face and body, or thinning hair on the scalp.

Women with PCOS often take birth control pills to regulate the menstrual cycle and reduce the level of androgens in the body as past research has indicated that pretreatment with a short-term course of birth control pills can raise pregnancy rates among women with PCOS.

The latest study examined the differences in pregnancy outcomes among 149 women with PCOS who either took birth control pills, underwent lifestyle modification or a combination of the two interventions for a four-month period.

The participants were between the ages of 18 and 40.

The researchers found that women who participated in the lifestyle modification intervention and took birth control pills were more likely to ovulate than women who were assigned to take birth control pills.

"The research indicates preconception weight loss and exercise improve women's reproductive and metabolic health," Legro said.

The study was published in the Journal of Clinical Endocrinology & Metabolism.