The demand, according to ads, is fueled by women willing to go to any length to get revenge on an ex, trigger a proposal, or “prank” friends and family. Pregnant women are cashing in, offering positive pregnancy tests and even bottles of their urine to facilitate a more realistic effect. Take this ad for example: “I am pregnant and am willing to take a pregnancy test for you that will be positive. Use it however you like no questions no judgments. I will take test right before you pick up. I will also be willing to bottle my urine if you need to seal the deal that way.” Whether or not foul play is involved, a healthy skepticism of positive pregnancy tests is warranted. “There is an occasional false positive. Guys should be aware of that,” says Mary Jane Minkin, MD, a Prevention advisor and clinical professor of obstetrics, gynecology, and reproductive sciences at Yale University School of Medicine. “But this is bizarre.”  More from Prevention: Migraines Change Your Brain 44%