The niche is actually bigger than you may think; as I am still part of a group of women who are pregnant or had babies recently, and the group is much larger than I would have thought. Kristen Armstrong’s workouts are testament to that as well, with 20-40 cyclists per workout which were framed around pregnant, postpartum, or women just not looking for something too intense.
Also, I have no science to back this up 
but I do believe Zwift has a much higher female to male ratio compared to TR; and although pregnancy and postpartum don’t last forever, it does happen frequently.
When pregnant, I just rode up the Alpe at 60-70% FTP most days. Structured workouts stressed me out so much; as I’m too type A to miss an interval…Postpartum my endurance was incredible! The instantaneous doubling of lung capacity, huge blood volume, and not being kicked in the ribs constantly also helped immensely! Baby doping is REAL! (minus all the time, effort, love, sleeplessness, and mental capacity you put toward keeping something so beautiful alive…)