Gas is a gas containing flammable components made from coal. Generally, if a pregnant woman smells gas occasionally, there is no major damage. If you smell gas frequently and often, it will affect the fetus. Because the gas contains a large amount of carbon monoxide and hydrogen gas. Especially carbon monoxide, for pregnant women inhale too much, resulting in a reduction of oxygen-binding hemoglobin in the body, and even cause chronic poisoning of carbon monoxide, so that the fetus also appears to lack of oxygen, causing intrauterine distress. A longer time this time, miscarriage may occur.