How should CPR be modified for a visibly pregnant woman who is 20 weeks or more along?

In the case of a visibly pregnant woman who is 20 weeks or more along, the correct approach is to position the woman on her left side. This modification is critical due to the potential for the uterus to compress major blood vessels, such as the inferior vena cava, when the woman is placed flat on her back. This compression can severely reduce blood flow to the heart and, consequently, the brain, which can adversely affect both the mother and the fetus during resuscitation efforts.

Positioning the woman on her left side helps to alleviate this pressure and improves blood flow, thereby enhancing the effectiveness of CPR. The other methods do not address the critical need to optimize circulation during resuscitation in a pregnant woman. Thus, modifying the position significantly enhances the chances of survival for both the mother and the unborn child during a cardiac event.