Is there any explanation as to why it seems like a high majority of Girls that I went to High School with aren’t with the father of their kids?

I’m “friends” with many of the girls I graduated high school with on some social media platforms. I’ve slowly began to realize the pattern that it seems like of those girls that have children, almost none of them are still in a relationship with the father of their child.

For context, the reason I’ve noticed this pattern is that almost every girl that’s gotten pregnant posts the “maternity shoot”, usually on a beach, announcing the pregnancy with the father. Then, sometime down the line after the baby is born, I’ll notice that there’s a new guy in the social media posts, or zero mention of the father.