It would make sense, especially for those who don't want to see it. I understand the pregnancy tag, but the birth tag would be a good warning for those who don't want to see that scene, while also adding (avoidable) so people can know if they can skip such a scene or not.
Most games with pregnancy tag just have creampie content. Other at least have girls begging to be knocked up. Rarely you get a picture showing the MC years later with children and a happy family as last picture. The content, where pregnancy really means a pregnancy belly and in the end a birth are rare. And I did not find any single game, where the story continues after birth. Maybe for a simple reason. The happy fantasy family or harem world would end with dirty diapers.
But I wish, pregnancy tag would require to see at least visible pregnancy.
Basically, you can add a lot of weird and interesting tags if you want, but at some point it will become hard to keep track of them. For example, I would add a tag for visual novels that meaning that you can see the thoughts of other characters besides the main character.