Talk about pregnancy and fertility often centers on how old a woman is when she begins having children and how many she intends to have. There’s less discussion on the other end of the female reproductive cycle: the age at which a woman has her last child. Researchers at Bowling Green State University in Ohio decided to take a close look at that, given the falling fertility rate in the United States and much of the rest of the world, which has ramifications beyond an immediate household. The beginning and the ending of having children are tied together in ways that shape the future economy, a woman’s ability to have the number of children she wants, the coming workforce and even whether neighborhoods build or shutters schools. Questions of maturity and resources — not all financial — come into play. And this particular landscape has been changing for many years.