Do you have a city that breeds like the people are in a constant state of orgy? There is no need to implement birth control to control your population. Just migrate to another city! Announcing the release of the Immigration mod in both standard and WoC formats. This mod has a new unit called the Immigrant. You use two population points from a city, which has a population of at least 10; to create an immigrant. The immigrant can go and join an existing city that has a population of less than 7. Joining a city adds one population point to that city. Best of all the AI can and does use immigrants effectively. Your cities will welcome immigrants with open arms. 
