Hi Stan, I tried the prenatal yoga classes at Como Shambhala (Forum Mall - first trial free) and Mother and Child Center (Tanglin Mall - trial $30) this week.
Como Shambhala is a proper yoga studio while Mother and Child uses an activity room. There were also fewer moms-to-be at CS (not sure if it was because I went to CS on Thursday evening and M&C on Sunday morning).
Both instructors are knowledgeable but the M&C instructor was not their usual instructor who's on leave until late April. I find that CS focuses more on helping you prepare for the labor/delivery, while M&C focuses more on bonding with the baby.
I'm going to be signing up for the package at CS just because the classes are smaller and they have proper equipment (blankets, belts, mats, etc). Both packages cost about the same. Hope this helps