chadwick's sign chadwick's sign chadwick sign is a bluish discoloration of the cervix, vagina, and labia resulting from increased blood flow. it can be observed as early as 6 to 8 weeks after conception, and its presence is an early sign of pregnancy. these colour changes were discovered in approximately 1836 by french doctor étienne joseph jacquemin (1796-1872), and are named after james read chadwick, who drew attention to it in a paper read before the american gynecological society in 1886 and published in the following year, wherein he credited jacquemin for their discovery.