Then Abraham prayed to God, and God healed Abimelech and his wife and his female slaves, so that they gave birth to children. For the Lord had completely closed all the wombs of the household of Abimelech because of Sarah, Abraham’s wife.
Genesis 20:17-18 (NASB)
Sarah was barren, and the consequence to Abimelech and his household was also a kind of barrenness. God "closed the wombs" of everyone in the land.
Here, when it says "because of Sarah," the words are literally "at Sarah's word."
This happened back in Genesis 12, too; the plagues on Pharaoh may have been through Sarah's spoken word.