There are things about one's life and especially about one's children that cannot be known in advance and to which it would be foolish to assume a right outcome or a wrong one. How, for example, could you possibly know whether you and your family would be better off having had a boy child and then a girl, or a girl first, or two girls or two boys? What would your standard for comparison be? Which child would you have given up in order to have had the imaginary right family? You might have thought you wanted a girl, and then gotten one not at all like the girl you expected—not gentle, not Barbie-doll loving, utterly unlike your childhood self. You might have thought that having one child of each sex was perfect, and then found that family harmony eluded you nonetheless. Certainly, the more precise your expectations of your children and the more convinced you are that those expectations can be met (indeed, that you deserve to have them met), the more disappointed you are likely to be. Without some humility in the face of the unknown and unknowable—without some fundamental willingness to accept and to love whatever child you get—parenthood would be a very different, and a lesser, thing.
One might think that all this would be obvious to anyone who was ever part of a family, or read a novel about one. But in an era when people can shop, online, for sperm and egg donors of specified height and hair texture and IQ—in an era, in other words, of consumer-driven, privatized eugenics—it's easy to forget about what we cannot control or predict. In this environment radical reproductive technologies tend to slide into use when someone wants them and can pay. There's always at least one fertility doctor out there who will do anything, no matter how risky or ethically dubious. Religious absolutists fume; free-market purists and biotech groupies celebrate; and the rest of us scratch our heads, troubled by a vague sense that something's wrong here.