GENDER AND PLACENTAL LOCATION. “Dramatic differences were detected in chorionic villi / placental location according to gender. 97.2% of the male fetuses had a chorionic villi/placenta location on the right side of the uterus whereas, 2.4% had a chorionic villi/placenta location to the left of the uterus.”
http://www.obgyn.net/articles/relationship-between-placental-location-and-fetal-gender-ramzi%25E2%2580%2599s-method