Fetal imprinting, perhaps. It'd be hard to quantify. But with all the societal shifts occurring around the 70's, economics drastically shifted. I'm not even going to pretend like I know anything about maternity, but with the constant slew of shit the modern human has to deal with, usually something somehow novel, I'd be willing to point fingers at a shift in the baseline hormone profile before during and after pregnancy. Particularly in fetal development. There's undoubtedly research on the effects of elevated glucocorticoid levels in pre-, during, and postnatal development. But that's only one end.