I had a female villager that was only used as a parent. Once she got to the age of 50 (the usual age where they stop having children) I moved her to research and changed her preference. When she reached the age of about 64 I put her preference back to parent so that when she died she would die as a master parent. I went through the usual thing of having to stop her from doing her parent thing on occasion while she was researching.
I turned the game off for about an half-hour, came back and saw that she had a baby at the age of 65.

Looking at the posts above, I guess there is no age limit in VV4. :P