Interesting thought, that through childbirth a woman can gain protection and healing. Does sound too good to be true, but it would be an intriguing partial explanation as to married (i.e. with children) women living longer than single (i.e. childless) women.
(If you’re talking men, that has a more straightforward answer: Married men eat better, sleep better, and are watched over more by their wives than single men are. The discipline from marriage also helps out. That’s why most men joke about marriage but seek it out: we men know the benefits and want them for ourselves.)
Also leads me to some thoughts on another “Too Good To Be True” idea: Abortion Leads to Breast Cancer (Too Good To Be True means it’s believed because it fits your beliefs, not because of any truth behind the claim.). If both end up proven to act in real life, I could see a link in the two: Breast cells that have changed partway to produce milk may be receptive to “foreign” stem cells which cause them to mutate.
But let’s remember: we’re talking possibilities, nothing even tested out. The Abortion/Breast Cancer link has been pretty much shown as almost nonexistent in studies (look at the link above; there’s a hint at mid-term and late-term, but nothing solid yet), while the post-childbearing healing powers of pregnancy are merely (widely) whispered about. Still, they’re ideas worth looking at, but only ideas. Nothing to base life choices around, yet.