So, the Bioethics Council has recommended that parents using IVF be allowed to use pre-implantation genetic testing to choose the sex of their children. And thinking about it, its hard to see why they shouldn't be. The biggest objection is the effect such sex-selection could have on the overall gender ratio. But when only 450 IVF babies are born in New Zealand every year, its hard to see this being a real problem.
What about the more general issue? Should we even try and select the sex of a child? Again, I don't see why not. Sure, it's "unnatural", but big deal. So is surviving past 25, living in houses and not being eaten by leopards, and very few of us have a problem with that (those that do should stand by their beliefs and form an orderly queue outside the leopard cage at the nearest zoo). More philosophically, any claim to an inviolable "natural order" runs smack into Hume's is-ought distinction, which basically says "you can't derive moral values solely from facts about the world" - you need some sort of linking premise. The classic ones are a simpleminded identification of "natural = good" (which falls over the moment anyone actually bothers to look at nature), or "god said so" (which might convince a rather stupid four year old, but is unlikely to convince anyone else, particularly if they do not share your imaginary friend).
So much for "nature". What about practical reasons? That brings us back to gender ratios. The ex-expat expresses concern about this, based on what has happened in China and Korea where sex determination and selective abortion have produced severe distortions. But as someone who doesn't think the "need" to perpetuate the human species justifies any intervention in people's reproductive choices whatsoever, I certainly don't think a mere gender ratio is sufficient (or the need to preserve blonde hair, green eyes, or any other part of the human gene pool). People's reproductive choices are solely their own, and no business of the state, no matter what. Yes, an imbalanced gender ratio would constitute genocide if it was the deliberate result of government policy. But if it’s the result of millions of individuals choosing to favour one gender over another, then it’s just Other People's Choices, and we just have to live with it.