Jabir reported the Jews would say: "Whoever goes into his wife's vagina from behind her, then his children will be cross-eyed." So Allah revealed: Your wives are a tilth for you, so go to your tilth when or how you will (2:223).
Sahih Muslim and Jami at-Tirmidhi
The ayah itself is evidence that allows men to have sex with their wives from any way.P
http://islam.stackexchange.com/questions/18749/is-doggie-style-sex-allowed