Targum zu Bereschit 30:21

And afterward she bare a daughter, and called her name Dinah; for she said, Judgement is from before the Lord, that there shall be from me a half of the tribes; but from Rahel my sister shall go forth two tribes, even as they shall proceed (in like manner) from each of the handmaids. And the prayer of Leah was heard before the Lord; and the infants were changed In their wombs; and Joseph was given to the womb of Rahel, and Dinah to the womb of Leah.