Leave it to Cersei to announce a pregnancy at a time like this, when big wars are on the horizon and there is literally no place for a baby in her life. And the reactions to Cersei's pregnancy on Game of Thrones show fans have no trust left for the queen, if they ever had it. If she is pregnant, did she ensure this to happen on purpose? And if not, is Cersei basically using a fake pregnancy as a ploy to get Jaime totally under her control? I wouldn't put either past her.
When Cersei revealed to Jaime that she's pregnant, she did it in a very Cersei-like way of coy dramatics, pressing her hands to her stomach and mentioning how they have to do what's right for their house. And with any other character on Game of Thrones, it would be believable, but the timing is far too perfect for Cersei to be pregnant with a baby she plans to openly admit is her brother's.
As Jaime recited their long dead father's saying, "The lion does not concern himself with the opinions of the sheep," Cersei made it clear to him that this time around, everyone will know who her unborn baby belongs to. But fans' reactions to Cersei's pregnancy on Game of Thrones show how much skepticism viewers have regarding the possible baby Lannister.
Jaime was in no way pulling back from Cersei while he urged her to consider a different approach to the war with Daenerys, but Cersei obviously took his words seriously after thinking it over. But is her alleged pregnancy a way to keep herself alive in the days ahead or has all of that Lannister incest resulted in yet another illegitimate child?
All of that said, I have no doubt that if Cersei is pregnant, Jaime is the father. History has proven that the queen likes to keep it all in the family when it comes to her bed partners. Her old flame, their cousin Lancel, joined the faith and died when the Sept blew up. There's been no indication that she's sleeping with anyone else, so if Cersei's truly pregnant, it's definitely Jaime's.
But back to the question of the pregnancy itself. This pregnancy feels really convenient for Cersei. Too convenient. Not only does it feel like a Lanniester marketing ploy, it helps her retain Jaime's loyalty when he has every reason to turn on or simply abandon her. Beyond that, there is very little reason to trust Cersei at this point. The pregnancy also doesn't coincide with Maggy the Frog's prophecy about having three children, as told to Cersei when she was a child.
Then again, she never specified if Cersei would have any out of wedlock, so it's not entirely impossible. It's just really too convenient timing for Cersei to be pregnant and because of that, Game of Thrones fans really aren't having it.