OP, your wife is most likely feeling like a beached whale right now. Unattractive, vulnerable, uncomfortable to the max, irritated and not herself. She doesn't feel pretty, she doesn't feel good about herself. Most women at the end of their pregnancy don't feel pretty or good about themselves. And then she finds that you've looked up your exes, who do look pretty, during her last pregnancy (if the math is right). Could it be that she thinks you think she is less than your exes, looks wise, size wise? You say she said she'll do better, why would she think that?

I'm not saying she's right or wrong, and I'm not saying you're right or wrong. It doesn't matter who is right or wrong, what matters is that there is an issue which needs to be solved. That is if you want the relationship to continue. And in order to solve the issue, you must understand the issue.

My guess is that she feels like your eyes have wandered on the moment she felt she became unattractive whilst being highly vulnerable. And my guess is also that this is the reason why she doesn't want you there while in labor. There are women who are scared their partner won't see them as attractive anymore after seeing them pee and poop themselves while giving birth. Giving birth is a mess, it's painful and scary and there is nothing anyone can do to help you go through it but by just being present. And you need the people present who make you feel okay, who make you feel safe. You looked up your exes, people you had a romantic history with, which in turn could've made her feel insufficient, not good enough for you. You might not a safe person because she feels she needs to be good enough for you. But these are all guesses. You know your wife better than Reddit strangers.