St. Margaret, called by the Greeks, Marina, was martyred at Antioch in Pisidia under Emperor Diocletian at the end of the Third Century. Devotion to her became very popular in Rome during the Middle Ages, and many chapels and churches were dedicated to her. She is invoked, especially, by those who are about to become mothers.
(Source: The New Roman Missal, Rev. F. X. Lasance)