The whitetail's reproductive rate is quite high when compared to the mule deer's, which is about 94 fawns per 100 does per year. Only about seven percent of mule deer does breed as fawns. A year later, 94 percent of whitetails and only 68 percent of mule deer become pregnant as yearlings. About 79 percent of pregnant whitetail does carry twins or triplets, while only 52 percent of pregnant mule deer does have multiple births.

Took that from a study that I found on-line
http://www.holoweb.com/cannon/whitetai.htm