As System Down said, no proofs so far. However, there is a popular theory suggesting that the prophecy understood to predict Daenerys' childlessness may be true, but in an unexpected way.... (potential spoilers for A Dance with Dragons below)
Note this part of the prophecy regarding Daenerys' childlessness: "When the sun rises in the west and sets in the east," said Mirri Maz Duur. "When the seas go dry and mountains blow in the wind like leaves. When your womb quickens again, and you bear a living child. Then he will return, and not before." It has been speculated that "the sun rising in the west" and "setting in the east" could refer to House Martell of Sunspear, whose House sigil contains a burning sun. Specifically, this could refer to the events of ADWD, and the Prince of Dorne's decision to send his son to Daenerys, to attempt to organise a marriage pact with Daenerys against the Lannisters (the sun "rising" against the crown in the west); and the subsequent death of Quentyn Martell at the hands of Daenerys' dragons (the sun (sun's son) "setting" in the east). The seas could be the Dothraki seas, going dry etc.. The fact that part of the prophecy can be held to have already come true, is interpreted by some people as meaning the rest of it will also come true. In this theory it is theorised that when Dany bleeds, this is her menstruating or possibly miscarrying - indicating that Dany is now capable of carrying a child once more, as foretold by the prophecy.