Men who undergo a vasectomy may have an increased risk of advanced or lethal prostate cancer, a new observational study suggests.

Researchers tracked nearly 50,000 men over 24 years, and found those who had a vasectomy were about 20 percent more likely to be diagnosed with aggressive or potentially fatal prostate cancer than those who had not had the procedure, FoxNews reported.

The researchers called this increase "modest," and said more studies of the possible link are needed. In other words, they don't think we should conclude from this that people shouldn't get vasectomies, because the absolute risk doesn't go up too much.  But it does show that there is something going on.

Vasectomies remain a common form of male contraception; the Harvard School of Public Health estimates about 15 percent of American men have had a vasectomy in their lifetime. So it could be that it only appears that men with vasectomies are more likely to get prostate cancer because these men undergo more PSA screenings to test for the cancer, or medical check-ups.

Besides, men get vasectomies in their 30s and 40s, and prostate cancer when they're 70, and so researchers feel like it's a very personal choice to decide about family planning when you're young and balancing that with cancer risk much later on.

However, men should talk to their doctors about regular PSA screening as they age.