Who wants three children? When is two not enough? Well, in Sweden it seems that couples who have one girl and one boy are the ones most likely to call a stop.
Professor of Demography Gunnar Andersson, at Stockholm University, says that in such a case, both a mother and a father would have a child that they can identify with.
So, if one of each is the perfect scenario - what would couples rather avoid? It seems that in Sweden it is most likely that parents with just boys will keep trying for a girl.
It is not a major difference, but according to Swedish Radio's Science Programme it is a tendency clearly measurable from the official statistics, and something that has been evident since the 1980s.
Ann-Zofie Duvander is a lecturer in sociology and demography at Stockholm University and tells Swedish Radio that the weak preference for girls may be connected to the way that children are currently seen - with more choice of girls' clothes, in a range of bright colours, compared to what's on offer for boys. Another reason may be that girls are often better at behaving responsibly in social situations, towards both young and old, which could make the idea of a baby girl a slightly more attractive idea.
But Duvander says that talking about a gender preference is very much taboo in Sweden and that this modern welfare state has come a very long way towards a situation where a child's gender simply does not matter.