Question: Which of the following statements is correct in describing a marginal placenta previa? Need Assignment Help? Question Answer a. Occurs when a portion of the cervical os is obstructed by overlying placenta. b. Occurs when the entire cervical os is obstructed by an overlying placenta. c. Occurs when the placenta's lower edge lies within 0.5 to 5 cm from the internal cervical os. d. Exists when the placenta extends up to, but not above, the internal cervical os.