Carbon dioxide. Carbon dioxide (chemical formula CO2) is a colorless gas with a density about 60% higher than that of air (1.225 g/L) that is odorless at normally encountered concentrations. Carbon dioxide consists of a carbon atom covalently double bonded to two oxygen atoms.
You should only do ballet in pregnancy if you are used to it. Ballet stretches can place a lot of pressure on your joints, especially your pelvic joints, and standing on one leg can cause pain in your pelvis.
Many pregnant women wonder whether plank exercises are safe in their condition. The answer to that is yes. Planks can be safely performed during pregnancy, provided you do them right, follow your doctor's guidelines on the best plank exercises suited to your condition, and more importantly not overdo it.