During pregnancy the abdominal muscles are stretched, the spinal column realigns to help the mom maintain balance, and the babies added weight gives mom more to carry. In other words, your back will hurt from weight and the feeling of lack of support. I have a history of back pain and during my pregnancies (especially my first) I felt constant pressure despite regular chiropractic adjustments.
I thought I would share a few poses that help stretch and flex the back.
Cat and cow are classic opening poses in many yoga classes. Start on your hands and knees. Hands should be shoulder distance apart with weight distributed evenly across the palm of the hand. Knees should be under the hips. Cow: Inhale, lift your head to look towards the sky, open your chest, and drop your belly towards the mat. Cat: Exhale, drop your head to look at your thighs and stretch the lower back lightly as you separate your shoulder blades away from each other. Do not over exaggerate these poses. At any point you can replace the cat with a neutral spine in the flow.
If you have a neck injury do not look forward or at your thighs, but instead keep your head inline with your torso
I personally found that due to my weight and acid reflux the classic cat-cow poses were not always comfortable. For those times, I simply replaced the poses with a seated spinal flexion/extension that may be performed on a chair or in an easy cross-legged position.
Spinal Extension on the Knees
This pose can be done with a chair, bench, or ottoman. Simply sit on your knees facing the chair and come up on your knees. reach towards the chair. You may need to readjust so that you are far enough away from the chair to allow your torso to be parallel to the ground and forearms resting on the chair seat.
Begin this pose on your hands and knees with your big toes touching. Exhale and sit back on your knees. You may choose to either separate your knees and allow your belly to rest against the ground or keep your knees together with your belly against your thighs. Reach your arms along the ground in front of you. This is a pose often used to rest but works well to stretch the low back muscles and can also function as a hip opener for those with tighter hip muscles.
Called "malasana" in sanskrit the wide squat was one of my favorite poses during pregnancy. Start in mountain pose, standing straight and evenly distributing your weight across your heals and foot pads. Exhale and lower your body towards the ground, if your heels lift that is okay. (See these instructions in order to understand just how far you need to lower;))
This is not an all-inclusive list. I specifically left off certain standing poses such as triangle pose and select twisting poses because twisting can be a contradiction to pregnancy depending on the pose selected and the manner performed.