Dunno, but I’ve been a coffee-drinking fool all my life and a fertile Myrtle to boot. Six pregnancies in six years. Although two only made it because of -rh factor, but no fertilization problem. Hmmmm....
Maybe some women are borderline for some particular reason or reasons. Maybe the caffeine will push them across the line. Something like that.
Trying to recall if I drank much caffeine in my hyper fertile days. I don’t think I did. Should have ;) (only kidding, wouldn’t trade my three rug rats who grew into fine young men for anything, not really).