Safe Abdominal Exercises for Pregnancy (2nd & 3rd Trimester)

Question
What are some good abdominal exercises that I can do to maintain some strength during the end of the 2nd and throughout the 3rd trimester?

Answer
Plank exercises and quadruped exercises, which stabilize the spine in the neutral position are all good, as well as pelvic tilts and Transverse Abdominis (TvA) isolations which can be done right up until labor and delivery.

For two safe standing variations for the TvA and pelvic tilts, go to:
http://befitmom.com/strength_training.html and scroll down to the bottom of the page.

Don't do any abdominal exercise that flexes the upper body off the floor against the force of gravity, like a crunch, or the Pilates one-hundred.