This idea is extrapolated from Hirsch Humash Breishis 1:28, New edition pm 46, S.V. "Umil'u"
It seems bepashtus that the mitzva of pru urvu is about populating the world by reproducing more humans than what were there before. This does not mean merely replacing, but adding on through increasing the numbers.
While women are technically exempt from this mitzva, their participation is essential nonetheless. Lasheves yetzarah also implies a quasi obligation upon women to participate in this goal.
Now let's step back and ask: what about those [men and women] who unfortunately are not birthing children due to various circumstances and limitations? What should the childless Jew do?
Approaching this from a communal focus - instead of from an individual focus - the resolution seems also "pashtus". Men and women who are not blessed with offspring can assist others in this noble endeavor.
The last mitzva in the Torah - kesivas Sefer Torah - is assigned to the individual. Yet, it is rarely accomplished by the individual anymore. It usually takes a a sofer, and often it "takes a village."
So too, with bringing up the next generation. The physical parents are analogous to the sofer, and so there is room for more participation. Several tasks that can be parceled out to the community at large include:
• Assisting the new parents by providing meals or "baby-sitting" relief.
• Medical and Nursing Assistance.
• Training or Coaching "new parents."
• Training children in Talmud Torah or in parnassah.
• Participating in synagogue youth work, such as minyanim, etc.
• Giving rides when necessary for parents or children - such as to the doctor or shopping.
• Playing surrogate "grandparents" when the children have none handy.
Anyway, the list goes on. The point of this exercise is to afford an opportunity for the community to adopt this mitzva so that all may be a part of yishuv olam. So those that cannot do for themselves can still enable others in this essential Mitzva.
A childless woman, "Tzipporah," has dedicated her life to teaching children in a Jewish Day School. In addition, as an aunt, she helps her nieces and nephews by playing the role of "surrogate grandmother". Thus both her personal and professional life participate in participating in or enabling the mitzva of Yishuv Olam.