I asked recently in the new mom's forum at my office what prevented them from having more children. Many women expressed that they would have loved to have 3-4 children instead of 1-2 but that the limiting factor was time. To have 3-4 children they would have needed to start in mid-late 20s but they and their partners could not get financially, professionally established in order to start a family at that age. Others said that the time-related logistics of multiple kids with two working parents aren't manageable beyond two. Daycare, school, extra-curriculars none of those schedules align well with working hours.