Perhaps it was this article -- where analysis of age-50+ members of a particular Amish community showed that lifespan of mothers increases linearly up to 14 children, and increases with later age at last birth:

https://www.ncbi.nlm.nih.gov/pubmed/16510865

(Interesting... it also shows a positive -- but lower/noisier -- effect for fathers as well, so there may be more at work than just stem cells.)

Just a friendly reminder that correlation != causation. Personally, I would bet that what's happening here is that healthier individuals choose to have more children, rather than that having more children increases life span.

Almost.

An evolutionary theory based guess is that healthy long lived individuals are more attractive in the mating arena and therefore have more children.

I think the Amish get married young and then stay married for life, so not sure if attractiveness plays a factor (since more or less everybody gets a mate).

> women that had like two or three kids, live longer on average than those that didn't

Can't have 3 kids if you died at age of 10.

While that's true, the context of the statement makes it clear that's not what's being discussed at all.

I assume they looked at groups of women, and controlled for partner presence.