If scientists invented a way to curb population growth in developing nations, would it be immoral to use it?

Say scientists invented nanomachines (microscopic machines) that could be put in the water supply of overpopulated and impoverished slums. These nanomachines would prevent women from getting pregnant solving global problems like overpopulation, food shortage, disease evolution and atmospheric carbon pollution. Would it be immoral to use this technology despite the unquestionable good it would do for humanity? Would organizations like the Catholics go crazy over this?