I had lunch today with a great Marian expert from Syria, a Greek Melkite Antiochian Catholic who is a professor at the Oriental Institute here in Rome. I asked him about the Eastern teachings and traditions about Mary’s giving birth to Jesus.
He responded that the tradition of a painful birth of the Lord by Mary comes from the Koran, not from the Eastern Christian tradition.
He said (in Italian) that the Koran speaks of "dolore del parto… the pain of childbirth". Also, the Koran leaves the issue of Mary’s viriginity in partu very vague. Clearly the issue of "pain" and "virginity" are conceptually connected in regard to the miraculous birth of the Lord. It is miraculous not merely by virtue of Mary’s virginal conception, but also miraculous by virtue of something very unusual in the moment of birth itself: painlessness.
In any event, since our faith seeks understanding and since we want to know what the Church really believes, we shall continue to dig away at this.