Just setting the record straight here:

Claremont introduced Valeria von Doom: the miscarried daughter of Sue and Reed that Doom went back in time to save, so he could show Reed that he was superior to him. She returns as a member to the team from the future having inherited her mothers powers for a while, basically being Rachel Summers.

Mark Waid later had her reborn in the current time, this time the child stayed with Reed and Sue (though Doom did assist in the birth in exchange for naming the child, so she is still called Valeria). Millar later reveals that young Valeria is hyper-intelligent, but does not have any superpowers (bit of contrast with Franklin, who has powers, but has normal human intelligence). That Valeria has been pretty much a mainstay of the FF for the last 10+ years.