Final answer:
Diaphragms have a relatively high failure rate due to factors such as incorrect insertion and positioning, discomfort of use, and vigorous sexual activity.
Step-by-step explanation:
The high failure rate of diaphragms can be attributed to a few factors, including incorrect insertion and positioning. When a diaphragm is not inserted properly, it may not effectively cover the cervix, allowing sperm to pass through and potentially resulting in pregnancy. Another reason for the high failure rate is the discomfort of use. If a diaphragm is uncomfortable or causes irritation, it may not be used consistently or correctly. Finally, vigorous sexual activity can also contribute to a higher failure rate of diaphragms. Intense physical movements can dislodge or shift the diaphragm, reducing its effectiveness.