Pregnant women are always dizzy and out of breath. What's going on?

Pregnant women always dizzy on the gas is considered because with the gradual increase of gestational age, fetal growth and development of the body size continues to increase, the uterus also increases with the growth of the fetus, the increased uterus compression heart, leading to diaphragm upward chest reduction, body hypoxia will also affect blood circulation, leading to dizziness on the gas.