Here's my thoughts.
SAI has no rule concerning this. We currently have a member who has a baby, and we had one who was married. They are great sisters and members.
However, the thing is, SAI is quite different from NPC sororities. We do a lot, but not like the NPC's. And because our groups are always smaller than NPC sororities, it's easy to scedule events around everyones lives...in fact, my chapter manages to scedule around one girl for her baby, me and 2 others for church, another for her Delta Zeta commitments, and others for jobs.
My advice to someone who wants to be Greek but is married and/or has a child...consider rushing a Non-NPC org...perhaps a professional like SAI, or a service org like APO. These groups are usually smaller and more willing to scedule around commitments you may have.