Name a physical sign indicating pregnancy that can be observed on examination.

Chadwick’s sign is a notable physical sign of pregnancy that can be directly observed during a clinical examination. This sign refers to the bluish discoloration of the vaginal mucosa and cervix, which occurs due to increased blood flow and vascular engorgement associated with pregnancy. It typically becomes apparent around the sixth week of gestation and is a reliable indicator that suggests pregnancy is underway.

This physical manifestation is particularly valuable in early gestational assessments. The observation of Chadwick’s sign requires a pelvic examination, making it a tangible sign that healthcare providers can note during visits.

In contrast, while a positive home pregnancy test indeed suggests pregnancy, it relies on biochemical markers rather than direct physical assessment. Hegar's sign, which involves softening of the lower uterine segment, is also a valuable clinical indicator but might not be as observable in a standard examination compared to the visible change represented by Chadwick's sign. Lastly, the detection of a fetal heartbeat via ultrasound, while an important confirmation of pregnancy, is a technological assessment rather than a physical sign. Therefore, the choice identifying Chadwick’s sign as a physical sign makes the most sense in this context.