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.
Exercises to Avoid. While most exercises are safe during early pregnancy, you should avoid certain activities all together. Avoid contact sports such as rugby, tackle football or wrestling during pregnancy. Additionally, stay away from activities with a high fall risk such as downhill skiing and skating.