Another good exercise for pregnant and after pregnancy=) This one strengthens the core and bum!
Lie down on the swiss ball and place your shoulders where it feels comfortable but not to steady. 90 degrees in the knees and a straight line from upper body to the knees. Important to push the hip up and tense core and bum. You can stand with the feet wide apart or narrow..harder with balance if you stand narrow=)
Rotate with arms straight and keep hips in the same position the whole time. Go back to start position and rotate to the other side. Repeat 10 times on each side. Rest 30 seconds and repeat again 2 more sets. To make it harder you can hold a weight, still on straight arms.