If a pregnant woman does not have a heart condition and feels out of breath when climbing stairs, the fetus will not suffer from oxygen deprivation. However, if the pregnant woman suffers from heart disease, the fetus may suffer from hypoxia. In the second trimester, as the fetus gradually grows larger, pregnant women will experience symptoms such as chest tightness and shortness of breath, and these symptoms will be more pronounced when climbing stairs or walking briskly. If a pregnant woman is out of breath simply because of an enlarged fetus, the fetus may not experience hypoxia. However, if a pregnant woman suffers from heart disease and her heart’s systolic or diastolic function decreases, it will affect the supply of oxygen and nutrients to the fetus, and the fetus may suffer from hypoxia. This is especially true when a pregnant woman is doing strenuous exercise, such as climbing stairs, when she can’t breathe, the symptoms of fetal hypoxia may be more pronounced. Pregnant women should pay attention to monitoring their own physical condition during pregnancy, and when symptoms such as breathlessness when climbing stairs, frequent chest tightness, shortness of breath, etc. occur, it is recommended to consult a doctor in a timely manner.