Yep. C-sections and infant formula are the main culprits.
Yogurt and breast milk...
We have a friend who has to have a c-section because she had to have one with her first baby. They’re going to deliver him by the end of the week, because he’s already 8 pounds, and mama’s not a big person and she’s been miserable for weeks. My daughter had to have a c-section because her baby had a shortened umbilical cord and the cord was wrapped around his neck. He has had several respiratory flare ups and is deaf in one ear, probably from laying on that side in the womb for 9 months. Thankfully, there’s nothing wrong with his brain; he’s smart as a whip! Usually, c sections are done because it’s required.
And C-sections often can’t be helped.
Needing to use formula rarely can’t be helped. There are the occasional reports of women who, for some reason, cannot produce breast milk, which must be heart breaking for them, because they clearly want to and tried before they realized they can’t.