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.
It is laughingly said that pregnancy is the best antidote to pregnancy; that you cannot get pregnant while you are pregnant. This is true in all but the rarest of rare cases. There are many reasons that a woman cannot get pregnant when she is already pregnant. For one a woman will stop ovulating once a pregnancy has occurred; also a mucous plug forms at mouth of the cervix, sealing off the uterus for all practical purposes. However there are freak occurrences in nature which make it possible for a woman to fall pregnant even while she is pregnant.