Jan 21, - WebMD dispels some common myths about pregnancy, fertility, and birth control. Washing or urinating after sex will not stop the sperm that have already to work with the woman's natural hormones to prevent ovulation. Aug 2, - Some old wives' tales turn out to be valid after all. found that the impact underwear choice has on semen isn't enough to affect fertility. For a man who has a normal sperm count, having sex every day during his partner's . you've gone between pees — and drinks — the more concentrated your urine.