It seems to me that the women who have problems are the ones who try to have their first child in their 40s. Women who have their first child in their 20s or younger and then have subsequent children in their 40s seem to get pregnant easier. Take Michelle Duggar. She had her first at age 22 and just had her 18th at age 42 and wants to keep going. My great-grandmother had her first in 1919 (my grandfather) at age 28 and her eighth (that survived) at age 44.
I often thought that might be the case.