Final answer:
Chadwick's sign is a bluish discoloration of the cervix, vagina, and labia that appears early in pregnancy, usually between 6 to 8 weeks, and is considered one of the secondary signs of pregnancy.
Step-by-step explanation:
Chadwick's sign is a physiological change often seen in pregnancy, specifically one of the earliest signs indicative of pregnancy. It is characterized by a bluish discoloration of the cervix, vagina, and labia due to increased blood flow and vascular congestion in the area. This change can occur as early as 6-8 weeks into the pregnancy and is considered one of the secondary signs of pregnancy, which although suggestive of pregnancy, are not definitive on their own. In clinical practice, Chadwick's sign is often observed during a pelvic examination and while it can be an indication of pregnancy, it should always be interpreted alongside other signs and symptoms as well as diagnostic tests such as a pregnancy test.