I am a student studying to be a Medical Sonographer in Oklahoma. I have studied many things about the human body. I have a story followed by a question. My parents were talking about something the other day that I believe is impossible. They were talking about this girl who got pregnant by wearing her married sisters underwear by wearing her panties after she had intercourse. I do not know why she wore those or how it even happened BUT my question is.. Is that even possible? I know sperm lives about 3 days in a woman's body. If the sperm is not in the human body, then it can live about 20 minutes in a warm and moist environment. I told my parents there is no way that could happen without the sister having intercourse with her sister's husband. I want written proof from a doctor because they won't believe me since I do not have a degree yet.