Wait... do people seriously think that global overpopulation is a problem? Honestly?
Now I know none of you are posting from Africa or Asia, where there is severe overpopulation problems, but none of you are talking specifically about those areas of the world either.
The West, where most of us come from and currently reside, has absolutely no current problem with overpopulation. Nothing, nadda, zilch. Any fears you have are drummed up by special interest groups (environmentalists being the main culprits), to gain support for their proposals. Governments love it because its a way for them to increase their power - just look at China for instance.
If you really wanted to curb population growth in the West, then you should be anti-immigration. They are responsible for most of the population growth in Western countries, both through arrivals and their above-average birth rates. Women in Western countries, on the other hand, are having so few children on average that in a couple of decades a population decline is expected. You don't notice this however because we keep on replacing the local population with immigrants.
In any case, overpopulation is a self-regulating problem, that is, once it becomes a problem, it solves itself. How do you ask? Well if there isn't enough for everyone to survive, then the excess members of the population will die, immediately rectifying the "overpopulation problem".
But still, if you're gullible enough to believe the world is in danger of being overpopulated, then just do what they did in the West - encourage feminism. It's the only proven way to reduce the number of children a woman has in her lifetime.