‘And she conceived again and bore a son, and she said, “This time will I praise (hodah) Yahweh.” Therefore she called his name Judah (Yehudah), and she ceased bearing.'
With three sons her confidence had returned. Everyone would be congratulating her. So when a fourth is born she can express praise to Yahweh. Her husband's God has been good to her and she acknowledges His goodness in the name of her son. The cessation of bearing is temporary (Genesis 30:17), although lasting for some fair period, so that she seeks to maintain her position by bearing children through her handmaid.