George Bush was explicit about it. He prohibited US funding of international groups that performed abortions or provided information about abortion. Harper's decision could have the same effect, depending on how it's implemented.
Say you have a poor country and there's an organization that provides maternal health services - it could be a clinic or a hospital or a group that covers several facilities. Say their services include family planning and/or abortion. Are they still eligible for funding under this plan?
Does someone work out what percentage of their budget is related to abortion, and then Canada asks some other country to fund that portion? That seems unlikely. But if not that sort of scenario, then it seems we must be disadvantaging organizations that support abortion. That's not just wrong; it's immoral.
It's beyond belief that a country that provides free abortions to its citizens would use its foriegn aid policies to prevent poor women in Africa from having abortions - especially since abortion is needed even more in poor African countries, where poor women have less control over their bodies and it is estimated that a third of pregnancy-related deaths are due to botched abortions.
Foreign aid is a tricky business. One of the reasons that sub-Saharan Africa is still so poor is the mess we've made with our foreign aid-slash-meddling. Just think of this scenario: there's a village with a maternal health clinic that's funded with western money, and now that clinic has been told that it won't be funded unless it ceases performing abortions - or even giving advice about them. Thanks to George Bush wooing the evangelical vote, that went on for eight years. Thanks to Stephen Harper wooing the evangelical vote, that might be about to start happening again.