Just a loose thought I'd like to share. Would love to hear those who disagree:
Assuming no birth control takes places - the poorest regions have also the highest population growth already and helping them would lead to more of the same, amplifying original problems of those regions creating bottomless well of help.
High fertility and death rates are normal for illiterate societies, this has been the way we lived for 1000's of years. The way to low fertility and low death rates is via basic education.