Sometimes, a decision that's even tougher to make than "Should we have a child?" is "Should we have another child?" -- and if the answer is yes, then the question becomes "When?" Sibling age gaps, AKA birth spacing, is a massive topic of analysis -- for economists, sociologists, the World Health Organisation, and most of all, parents, who must strategically weigh factors from finances, to their careers, to the annoying "clock", to the type of relationship they envision for the kids themselves. And then of course, the decision may not be in their hands at all, as it isn't like you can simply pick a date on the calendar and type in "new baby". It's very complex and very personal.