Game of Thrones has been very careful throughout the years to avoid most of the visions, flashbacks, and prophecies that practically litter the original A Song of Ice and Fire series. One of the very few we have seen is Cersei Lannister, as a child, visiting the woodwitch known as Maggy the Frog. But her prophecy, that Cersei would only bear three children, is now in doubt with her new pregnancy. Which leads us to ask if it's related to the half of the prophecy that the show left out: Is the valonqar Cersei's baby?
We should be clear that though the Maggy the Frog scene in the books included what is known as the prophecy of the valonqar ("little brother"), it was not included in the show. The show only showed Maggy telling Cersei she would have three children to Robert's 16, which are facts that were already established long before -- that Cersei and Robert did not have any children together, but he sired more than a dozen bastards, while she had three babies with Jaime.
That's a deliberate choice, to only show the prophecy that has already come true. This way, the show doesn't have to lock in a future it might not want later. But with a new baby on the way, was the Maggy the Frog prophecy they showed even right?
Since Game of Thrones was so firm as to actually use this prophecy in the show, we have to assume yes. Cersei will only have three children. This means the one in her belly isn't going to be born. It's either going to die in the womb, miscarry, or die as it's being born.
All three of those are incredibly dangerous situations to a mother, especially one who is older, and whose health might not be in the greatest of shape because she drinks a lot. Dying in the womb means Qyburn basically giving her an abortion. Miscarrying could cause her to uncontrollably bleed out. And as for a child coming into the world stillborn, that's as likely to kill a mother in childbirth today as it was in the sort of medieval times that Westeros lives in.
All this leads us to the newest theory: The baby in Cersei's womb is the valonqar "little brother" who will kill her.
Cersei has always believed that the prophecy's "little brother" is Tyrion. (It's why she hates him.) This is because she totally overlooks that Jaime is also her little brother. (By only a few minutes, but still.) The most popular theory is that Jaime would finally lose it and do the deed himself, or find himself in a "Mad Queen" situation, and slay her for the good of the realm.
But what if the "little brother" is the little brother to her three born children, the one who won't live, and will take her with him when he dies?
Or, because it was Jaime who impregnated her, is this how he (accidentally) will kill her?
We'll first have to see how Cersei's pregnancy is coming along when we finally get back to King's Landing, and if the baby survives to make it to Season 8. But it's certainly a new twist on how this long-standing theory could play out. Considering the show's been giving us unexpected twists to the answers of long-standing theories lately (like who the dragon's third head is), it might be high time we consider every possibility there is.