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Pregnancy Could Help Prevent Bladder Cancer
Researchers have found that women who have never been pregnant may be up to 15 times more likely to develop bladder cancer.
The US scientists were looking at a fact that has puzzled doctors and scientists for decades: Why does bladder cancer, one of the most common cancers, affect about three times as many men as women?
Scientists long blamed men's historically higher rates of smoking and greater exposure to dangers in the workplace, but the gap has remained even after women swelled the workforce and took up smoking in greater numbers.
Instead, they found that pregnancy seems to confer protection against bladder cancer.
"While some researchers have asked why men are more vulnerable to bladder cancer, perhaps we should be asking why women have more protection," said Dr Jay Reeder, a research professor at the University of Rochester Medical Center. "When it comes to bladder cancer, being female is a very good thing."
Investigator Aimee Johnson was investigating ways in which hormones might make males more vulnerable to bladder cancer. She was comparing rates of bladder cancer in male and female mice when she took a closer look at the females. She found an unexpected, marked difference in cancer rates and volumes among the female mice.
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Female mice that had been pregnant repeatedly had far fewer bladder cancers than both their normal male counterparts and their female counterparts that had never gotten pregnant. On average, mice that had never gotten pregnant were 15 times more likely to get bladder cancer compared to mice that had been pregnant.
"We were shocked at the differences between the two groups," said Reeder. "These mice were specially susceptible to bladder cancer, yet we saw virtually no cancer in the females that had become pregnant. The mice that were pregnant nursed their offspring, and a protective effect could be related to pregnancy, lactation, or both."
While scientists do know that early onset of menopause increases a woman's risk of getting bladder cancer, pregnancy hasn't yet been considered a possible factor in determining bladder cancer risk, said Reeder.
The results highlight a possible role for hormones in bladder cancer, perhaps like the known role hormones have in the development of breast cancer. Most hormone research in bladder cancer has focused on male hormones such as testosterone and their capability of boosting the cancer process.