The term "placental sign" denotes:
All pregnant females have amenorrhea. In a few pregnant females however, cyclic bleeding may occur upto 12 weeks of pregnancy, i.e. until the decidual space is obliterated by the fusion of decidua vera with decidua capsularis. Such bleeding is usually scanty, lasting for a shorter duration than her usual cycle and roughly corresponds with the date  of the expected period. This is termed as placental sign or Hartman sign.
Alteration of FHR on pressing the head into the pelvis
Spotting on the expected date of period in early months of pregnancy
Permanent lengthening of the cord in 3rd stage of labour
Slight gush of bleeding in third stage of labour