As the internet has already pointed out, we've been lead to believe that Daenerys probably can't have kids due to a kinda-sorta-maybe curse. Long story short: In George R.R. Martin's books, a witch named Mirri Maz Duur tells Dany that Khal Drogo won't return to her until her "womb quickens again" and she bears a "living child." The show left this line out, presumably to hammer the point home that kids aren't on the table.
BUT, per usual Reddit got its investigation on, and reminded us that Mirri Maz Duur also says "only death may pay for life."
"The latest episode mentioned Dany's heir and being infertile a HELL of a lot. As we all know, Dany sees her Dragons as her children. Mirri Maz Duur in Season [One] says to Dany 'Only death may pay for life.' So, what if all the talk of heirs and one of Dany's 'children' dying means she will now be able to conceive a real, human child after paying for life with death?"
Users have pointed out that the concept of death paying for life has been proven in Dany's story arc before:
Ergo, if Dany's dragon is dead (well, technically a zombie), she may be able to have a human child after all.