This pose is called warrior pose and is a great exercise for opening hips. You can perform this pose during third trimester and you may use chair for support, and the wall to help you with the balance.
Spread your feet wide apart and start with feet parallel. Inhale and raise your arms to the shoulder height. Exhale and turn left to the wall and point your left toes to the wall.
Bend your left knee and come closer to the wall.
Press the back edge of your trail