The Derry-born screenwriter shared the personal post on social media after having a caesarean birth at St George’s Hospital in west London.
She told Twitter: “Thought long and hard about posting this photograph as it’s so personal but all hail the NHS and thank you @StGeorgesTrust.”
The hospital features in Channel 4 show 24 Hours in A&E.
Nicola Coughlan, who plays Claire in the BAFTA-nominated hit Channel 4 comedy series Derry Girls, congratulated McGee: “Welcome darling boy!!” to McGee’s Twitter post.
In April, Channel 4 announced that it had commissioned a third season of Derry Girls.
However, filming is not expected to start until sometime in 2020 so the third series could have an autumn.
In an interview with the Radio Times a few months agp, Lisa McGee said that the new episodes will be set in a more hopeful period for the gang, as their hometown marches towards peace and the Good Friday Agreement of 1998 (where the writer suggested she would like to wrap things up).
Said the writer: “I’m just thinking about storylines at the minute. I have a political back story I want to do. It’s a bit scary but I’ll have to start writing things down soon.
“We’ll continue from ’95 so obviously it was very different for us then, for one thing all these splinter organisations came out of nowhere, which was quite strange, and then people were just getting used to peace time.“They had more to lose, I think, and we didn’t want it to go wrong because it was something we all really wanted.
“It was something everyone was afraid to dream of and then it was happening, so it’s scarier in a way, the idea of losing that.”
McGee is married to actor Tobias Beer.
The couple already have a three-year-old son.