SOLOMON B. FREEHOF
In general, one may sum up the law by saying that a woman who is generally considered old(i.e., by their standards in those days) has the same menstrual status as a young girl. With a young girl, if three, regular, successive periods have not yet occurred, she is not to be considered as having menstrual maturity. So an old woman, if she misses three regular periods, is no longer to be considered as regular.
This is about all there is(or at least all I can find) on this question.
1963).