Okay, kiddo, so when we talk about "maternal mortality" in fiction, we're talking about instances in books, movies, or TV shows where a character who is pregnant or has just given birth dies.
It's important to understand that this isn't something that happens all the time in real life, but it used to happen more often in the past when doctors didn't know as much about how to take care of pregnant women. Now, thankfully, it's much less common, but it still happens in some parts of the world where women don't have access to good medical care.
When it happens in fiction, it's often used as a way to show how dangerous and scary childbirth can be, and to create drama or tension in the story. It can also be used to show how strong and brave a character is in the face of a difficult situation.
It's important to remember though, that even though it happens in some stories, it doesn't mean that all pregnant women are in danger. Most women have healthy pregnancies and give birth to healthy babies with the help of doctors and nurses who know how to take care of them.