Which of the following is a caution to consider during Sirsasana (Headstand Pose)?

During Sirsasana, or Headstand Pose, caution is particularly warranted for individuals with osteoporosis. This condition makes bones fragile and more susceptible to fractures. In Headstand, the entire body weight is supported by the head and neck, which can strain these areas if the bones are weakened. Therefore, practitioners with osteoporosis should avoid this pose to prevent potential injury.

While recent surgery, pregnancy, and chronic headaches also present concerns, they are not specifically related to the structural integrity of bones in the way osteoporosis is. Recent surgery may involve other limitations based on the type of surgery and recovery needs, but it doesn't inherently affect bone strength. Pregnancy can introduce various modifications and considerations in yoga practice, yet it is not as directly linked to the risk of bone fractures as osteoporosis. Chronic headaches may be aggravated by inversions like Headstand, but this would generally not compromise bone stability. Thus, osteoporosis stands out as the most critical caution to consider in this context.