Daenerys Targaryen and Jon Snow ended up ~consummating~ their flirt-lationship in the Game of Thrones Season 7 finale, delivering the world's most unsurprising plot twist. But there are still some real surprises in store, like the question of whether Dany is pregnant on Game of Thrones. It's a strong fan theory, but honestly, it would be an extremely complicated storyline to introduce with just six episodes left.
Most of the evidence supporting a Danaerys pregnancy comes down to several references made to her fertility in the last three episodes of Season 7. As Cosmopolitan pointed out, it felt too heavy-handed to be a coincidence. Sure, she was ostensibly just making sure Jon understood that she'll never have children before they started a relationship — but that's also a pretty obvious red herring, no?
Back in Season 1, Daenerys sacrificed the life of her unborn baby Rhaego to save her husband Khal Drogo's life with the help of a witch who practiced blood magic. The baby was stillborn but Drogo was revived in a vegetative state. When the Mother of Dragons asked the witch Mirri Maz Duur when Drogo would return to his normal state, she replied, "When the sun rises in the west, sets in the east. When the seas go dry. When the mountains blow in the wind like leaves."
But! That particular Game of Thrones scene left out a very important line from the books. In the books, Mirri Maz Duur continues, "When your womb quickens again, and you bear a living child. Then he will return, and not before." In other words, Daenerys understands that Drogo will never return, and that the witch is saying she'll never have children. Such was the risk of the blood magic she invoked.
Even though that line was cut from the series, Daenerys still seems to understand she's barren, making several references to the fact that her dragons are the only children she'll ever have. It's been suggested that the final line of Mirri Maz Duur's prophecy was intentionally left out of the series to leave the door open for Dany to possibly conceive again. Another piece of evidence supporting the idea that Daenerys is able to defy the witch's prophecy comes from a passage in the books hinting that Daenerys suffered a miscarriage after Rhaego, but before meeting Jon Snow.
On the other hand, a Jonerys baby would be kind of a mess. The pair still don't know that they're technically aunt and nephew, but will probably find out as soon as they reach Winterfell. Bran and Sam — the only two people who know Jon's true parentage, thanks to a Three-Eyed Raven vision — are there, waiting to tell him. Furthermore, Daenerys is about to head into battle against The Night King. Is she really going to ice zombie war with a baby on board? It would almost certainly preclude her from taking part in the action, or else risk fans rolling their eyes at the unlikelihood of the scenario.
It just doesn't seem like there's enough time left to really develop a baby storyline, but one thing is certain: if Jon and Daenerys did have a baby, it would have the strongest claim to the Iron Throne of anyone.