The problem is more than just fertility - raising children is harder when one no longer has the energy of youth, or grandparents that are still healthy enough to help. Two generations of giving birth at 40, means the new child's grandparents would be 80 years old. Instead of getting help raising their children, the new parents have to look after both their children and their ailing grandparents.<p>Such children would also barely get to know their grandparents - by the time the kid is 10, the grandparents are 90, if they're even still alive - only 24% would be: <a href="https://www.ncesc.com/geographic-faq/how-many-americans-live-until-90/" rel="nofollow">https://www.ncesc.com/geographic-faq/how-many-americans-live...</a>