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.
In brief: Yes, but... As far as i can tell, bikram yoga is safe while pregnant. It is wise to avoid getting overheated during pregnancy so avoid hot tubs & saunas, but the amount of heat in bikram is not dangerous. But certain yoga postures should be avoided in pregnancy, while others are especially good.