Penn State University scientists found the continuous oral contraceptives might be better at suppressing the ovary and producing a significant improvement in pain and behavioral changes.

"We have provided a biological proof of concept that both the ovary and the lining of the uterus are suppressed better and quicker with the continuous pill than with the cyclic pill," Dr. Richard Legro said. "And there is no harmful effect on the lining of the uterus either."

The researchers monitored 62 women, randomly assigned to receive either cyclical or continuous birth control pills, for six months.

They found a significant decrease in moderate to heavy bleeding days among women who received the continuous birth control regimen. Women in the continuous group also had a significant decline in circulating and urinary estrogen levels, total ovarian volume and lead follicle size -- all biomarkers indicating the ovary is less active -- and they also reported less pain and behavioral changes compared with women in the cyclic group, the scientists said.

The research appeared in a recent issue of the Journal of Clinical Endocrinology and Metabolism.