I do not have a citation, but I was under the impression in hunter gatherer societies children were born about 3-5 years apart. That means if a woman started having kids at 15, she would have about 4-8 total in her life.
But that is in situations without medical care, and with limited resources. Plus I’m not sure how valid that claim is anyway.
Doesn’t a woman hit menarche in her early teens and reach infertility in her late 40s? The older you get, the harder it is to get pregnant but there are ways around it too. That gives about 35 years of fertility.