I googled it and found this:It is a theory based on which side the baby implanted on (so placental location and NOTuterus) and one that can be theorized extremely early in the pregnancy. You would need an ultrasound of 6-8 weeks, and ask your provider where the placenta is located/implanted.RESULTS:If the baby implanted on the left = girl! 97.5% of females implant on the leftIf the baby implanted on the right = boy! 97.2% of males implant on the right sideBe careful, though! Depending on which style of u/s you had done, it can change the results. If you had an abdominal ultrasound, it is mirrored. So if your placenta is on the right, that actually means it's on the left (which would indicate GIRL). If your placenta is on the left, that means it's actually on the right (Which would indicate BOY). If you had a transvaginal u/s, everything is exactly how it is in your uterus, so left placenta = GIRL and right placenta = BOY.Remember though that this is NOT fool proof and it's more for FUN! The ONLY sure proof way of finding out baby's sex is at birth ;)