There have been a number of instances in the Bible where the Spirit of God has acted in a birth. For instance, in the story of Abraham and Sarah, Sarah was too old and Abraham was also old. But the Bible says God quickened the womb of Sarah so that she could bear a son. In the same way, the Holy Spirit worked with Mary. It was not done in the sense of producing a child from the union of God with man, but in the sense of God participating in the event. Jesus was born of a father and a mother, just as anyone else is, but in his case the Spirit of God was working also.

Master Speaks (1967) Part 7: Bible Interpretation, (transcriptions of Q&A sessions in March-April 1965)