I'm not convinced about the "pains of childbith" angle. Our Lord and Our Lady took on many of the sufferings that they would normally have been exempt of due to being free from Original Sin. Suffering and death in general are the consequences of Original Sin, but they willingly accepted them anyway. I didn't watch this movie nor do I intend to, but if they depiced Our Lady as screaming/shreiking, etc., then that would be completely out of line, as I'm sure she bore whatever suffering she did experience with full dignity.