You can do this exercise, pregnant or not!! This will work your shoulders, core and rear end/legs!!
Get on all four’s. (Do this on a mat or towel if this bothers your knees) Take one light weight (2-5 pounds) in one hand. Lift your arm with weight straight out beside you while extending the opposite leg behind you. (As seen above) Bring the arm back down to beginning position while simultaneously bringing your leg towards your chest. Repeat.
Be careful to keep your lower back supported as much as you can. Draw the abs (from what you can feel!) in tight. Breathe and keep the gaze straight down to the floor. Be sure to switch sides after doing all reps on one side!
Do 2 sets (each side) of 8-12 extensions!