March 22, 2017 -- Women worldwide who take birth control pills should be reassured, doctors say, by a new study that shows they are not putting themselves at a higher risk of cancer. In fact, the pill may protect against some cancers.
The findings are the latest to emerge from the Oral Contraception Study, which was established in 1968 by the U.K.-based Royal College of General Practitioners (RCGP) to investigate the long-term effects of birth control pills.
At the start of the University of Aberdeen study, the pill was still a relatively new type of contraception, having first been introduced in the US in 1960.
Concerns were expressed early on about whether the pill could cause cancer. These concerns led generations of women to question the possible risks to their health from choosing this method of birth control.
A number of studies have examined a potential link between the pill and different types of cancer. The results collectively suggested that women who are or have been recently on the pill have a higher risk of breast and cervical cancer. On the other hand, they seem to have a lower risk of uterine and ovarian cancers.
These studies suggested the effects lasted for many years after women stopped taking the pill. They also suggested current users gained protection from colorectal cancer, although it wasn’t clear whether this protection lasted after women stopped using the pill.
For the U.K. study, 46,022 women were recruited and their health followed for up to 44 years. This makes it the world's longest-running study into the effects of the pill.
An analysis of the data, published in the American Journal of Obstetrics & Gynecology, found that taking the pill led to:
- A 19% lower risk of colorectal cancer
- A 34% lower risk of uterine cancer
- A 33% lower risk of ovarian cancer
Also, these protective effects have been shown to last for at least 30 years after taking the pill.
The study found current and recent users of the pill had a 4% increased risk of breast and cervical cancer, but that “appeared to be lost within approximately 5 years of stopping oral contraception” and did not go back up over time.
The researchers also examined the risk of all types of cancer in women who have taken the pill. This showed that using the pill during reproductive years does not produce new cancer risks for women later in life, when cancers become more common in the population as a whole.
"Millions of women worldwide who use the combined oral contraceptive pill should be reassured by this comprehensive research that they are not at increased risk of cancer as a result -- and that taking the pill might actually decrease their risk of certain cancers," RGCP chair Professor Helen Stokes Lampard says in a statement.
However, she adds: "This is not to advocate that women should be given the pill as a preventative measure against cancer, as we know that a minority of women do have adverse health effects as a result of taking the pill. Ultimately decisions to prescribe the pill need to be made on a patient by patient basis, but this research will be useful to inform the conversations we have with our patients when discussing various contraceptive options that are available."