The new generation of low-dose oral contraceptives do not have the same ability to cut the risk of functional ovarian cysts as did the older, high-dose pills, according to a report in the August issue of Obstetrics and Gynecology.

In a potentially more troubling finding, the study also suggests that tubal ligation, or having your "tubes tied", may increase your risk of developing these cysts by as much as 70%.

"Our finding about the new low-dose pills echoes what has been found in some previous studies, but it's amazing how many doctors continue to prescribe by the 'old rules'," says study author Victoria Holt, a professor in the department of epidemiology at the University of Washington.

The finding concerning cysts and tubal ligations - a surgical procedure that blocks the path from the ovary to the uterus so eggs can't be fertilised by sperm - was totally unexpected, Holt says. "This was shown in only one other study before," she says. That study was a small Mexican research project published in 2000 that found tubal ligation doubled the risk of a woman developing ovarian cysts.

Functional cysts commonly occur around midcycle, when a follicle destined to become an egg fails to mature. Instead of leaving the ovary in the process known as ovulation, it remains inside, floating in a tiny sac of fluid. It is that sac that eventually forms into a cyst. Although rarely malignant, ovarian cysts lead to 200,000 hospitalisations in the US each year. For some women, the cysts develop cycle after cycle, previous studies have shown.

Because birth control pills block egg development and ovulation, Holt says they were used intuitively by doctors for many years as a treatment to stop the cysts from forming. But the advent of the new, lose-dose oral contraceptives changed that presumption. While the new pills still contained enough hormones to block ovulation and prevent pregnancy, they were no longer potent enough to override the body's own chemistry involved in cyst formation, Holt believes.

For gynecologist Dr Rachel Masch of New York University, the new finding is no surprise because evidence has been mounting for some time that low-dose pills do not affect cyst formation. She adds, however, that because the study found a small number of women for whom the treatment worked, there remain some circumstances under which she might still prescribe birth control pills for this purpose.

"If a woman wanted to use a pill for contraception, or to help clear her skin, for example, and she also had recurring cysts, then it is still reasonable to give it a try as a treatment," Masch says. In most cases, though, other hormonal treatments are more likely to help.

As for the finding about tubal ligation and cysts, Masch says she's not convinced the association is strong enough to recommend against the procedure - one of the most popular forms of birth control in the US. "I certainly wouldn't advise a woman not to have tubal ligation based on this finding. But I do think it's worthy of a closer look," Masch says.

Holt's study, funded by the National Institutes of Child Health and Development, involved more than 1000 women between the ages of 18 and 39. They included 392 women diagnosed with functional ovarian cysts, and 623 cyst-free women who formed the comparison group. None of the women in this group was using any hormonal or surgical contraception, and most were using no contraception.

To document low-dose pill use and cyst development, the researchers interviewed the women in person, something not done in previous studies on the subject. The interviews were corroborated by the women's medical and pharmacy records.

Then, using a method of mathematical calculation, the researchers computed the odds that would link the use of oral contraceptives with either cyst reduction or formation. Factors that could influence the outcome, including a history of cysts or smoking, were included in the analysis.

The result: While the new low-dose pills didn't increase the risk of cysts, they also didn't help prevent them in the overwhelming majority of women. Only 28% of the women diagnosed with cysts found relief on a low-dose pill - a dramatic drop from the 90% plus effectiveness rates seen with the older oral contraceptives.

Additionally, the study found a 70% increased risk of cyst formation in women who had tubal ligation. Holt says she has no immediate explanation for this finding, and is calling for more research in this area. (Health Scout)

By Colette Bouchez
HealthDay Reporter

Originally posted week beginning 4 August 2003

Disclaimer

This is a summary article from Health Scout. Knowledgeable New Zealand health consumers may also find this article useful. This information is intended solely for New Zealand residents and is of a general nature only and no person should act in reliance on any statement contained in the information provided and at all times should obtain specific advice from a health professional. All rights reserved. © UBM Medica (NZ) Ltd. This publication is copyright.