Meaning: The time from conception to childbirth.
Genesis 18:14
Is any thing too hard for the Lord? At the time appointed I will return unto thee, according to the time of life, and Sarah shall have a son.
2 Kings 4:16-17
And he said, About this season, according to the time of life, thou shalt embrace a son. And she said, Nay, my lord, thou man of God, do not lie unto thine handmaid. [17] And the woman conceived, and bare a son at that season that Elisha had said unto her, according to the time of life.