Which of the following is a possible cause of early pregnancy bleeding?

Cervical bleeding from unrelated causes is recognized as a possible cause of early pregnancy bleeding because the cervix can be sensitive and may bleed due to various factors, such as infections, cervical polyps, or trauma. In early pregnancy, hormonal changes can also make the cervix more vascular and susceptible to bleeding, especially after intercourse or a pelvic exam.

Other options represent less likely causes in the context of early pregnancy bleeding. Intrauterine device removal can lead to bleeding but is not a direct cause of bleeding in a confirmed pregnancy scenario; rather, it may cause bleeding associated with the removal process itself. Younger maternal age is a demographic consideration but does not directly correlate with a cause of bleeding. Increased physical activity is typically not associated with early pregnancy bleeding unless there are underlying complications or conditions present. Thus, while they may be relevant in general discussions about pregnancy, they do not specifically account for early pregnancy bleeding as effectively as cervical bleeding from unrelated causes does.