The women answered questions about pain. Twenty-seven percent of those on a low-dose pill had pelvic pain symptoms or reported chronic pelvic pain compared to 17.5 percent of those not on the pill.
Those on normal-dose pills were less likely to have pelvic pain overall than those not on the pill, she found.
Low-dose pill users were twice as likely to report pain during or after orgasm than those not on the pill: 25 percent versus 12 percent. Those on higher-dose pills reported no difference in pain at sexual climax than those not using birth control pills.
Dr. Christopher Payne, a professor of urology at Stanford University School of Medicine and director of its division of female urology, said the information could be helpful. However, "I don't know if we can draw any conclusions from this," he added.
"You can only say there is an association [between the low-dose pills and pelvic pain]," he said. "You can't say it's cause and effect."
However, "it's certainly something people should be knowledgeable about," he added. The proposed mechanism -- that the lower estrogen somehow is linked with the pain -- is plausible, he said.
"We have observed people who have bladder pain say they often have flare-ups in the premenstrual period, which is the lowest estrogen level of the whole menstrual cycle," Payne said. However, some women also report pain in other parts of the cycle, he said.
"This information could help clinicians be aware there could be a connection between a woman's hormone level and her hormone therapy and their pain," Payne said.
However, he and other pain specialists see a subgroup of women -- those who have pain problems. Many women on the low-dose pills could be experiencing no problems at all with the lower estrogen levels, Payne said.
Women using low-dose pills who do experience pain might ask their doctor about switching to another contraceptive or using a higher
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