Gen 20:1 And Abraham journeyed from thence toward the south country, and dwelled between Kadesh and Shur, and sojourned in Gerar.
There Abraham said that Sarah was his sister (again!), so the people in Gerar took her. It is interesting to know that Abraham told the same lie for the second time regarding Sarah after the LORD and two angels visited Abraham and told him that Sarah will have a baby. Then God visited the king in his dream and told him not to touch Sarah. (Then it is clear that Isaac was not from this king.)
Then Abraham prayed for him.
Then what happened?
"God healed Abimelech, his wife and his slave girls so they could have children again".
To me, it looks like what God just did was to show Abraham that God was able to close and open the womb. I wonder what Abraham thought of this! He was getting too old, yet God confirmed that Sarah was the one to have the baby. Then he lied, putting Sarah in danger underAbimelech. Yet it is clear in the scripture that Sarah was untouched. Then God told Abimelech that Abraham could pray for him. When Abraham prayed, Abimelech's wife and his household could have babies!