A member of the SGU forum asked the following question:

I have a daughter that I love so much. But since I can not afford 20 more children and probably will only have one more, I would like to have a boy baby (Specialy my mom) hehe … many books on internet / and even doctors claim that they can help couples choose a certain gender. Is that a scam or can we really choose our next baby’s gender?

The short answer is that it is a scam (unless we are talking about artificial insemination, which I will discuss below).

First, some basic biology. Human DNA is divided into 23 different chromosomes, with each cell having a pair of each. One of those chromosome pairs are the sex chromosomes – which come in two flavors, X (female) and Y (male). Females have two X chromosomes, and males have one X and one Y. Eggs from the mother and sperm from the father each contribute one copy of the 23 chromosomes. Eggs can therefore only contribute an X, while 50% of sperm with be X and 50% Y. Therefore the sperm dictates the sex of the child.

Methods for influencing the sex of the child therefore focus on affecting which type of sperm, X or Y, fertilizes the egg. During insemination 10’s of millions of sperm are ejaculated with one ultimately fertilizing the egg. Various methods have been claimed to give an advantage to one type or the other. Some methods are based upon the fact that X chromosomes are slightly bigger than Y chromosomes, so it is believed Y sperm swim a bit faster. Methods include changes in diet, the timing of sex, and acidifying the vaginal canal. None of these methods are very plausible and none have been shown to be effective.

There are also countless “magical” methods that have been advocated over the centuries – methods without any putative biological mechanism but are little more than superstition.

The strong desire of many parents to choose the gender of their baby has spawned an industry of products and claims, but they amount to little more than snake oil and scams.

However, in the context of in vitro fertilization choosing the sex of the child is very possible. There are several methods that work well. You could fertilize several eggs, then do genetic testing to determine their sex prior to implantation. There are also methods for separating X sperm from Y sperm (mostly taking advantage of the different size of the chromosomes) and then fertilizing the egg with the sperm of the desired sex.

In vitro fertilization is expensive and time consuming, so only couples who cannot conceive naturally are likely to avail themselves of these methods. It is possible, though, for sperm separation techniques to eventually be available in a home kit, with insemination then taking place “turkey baster” style. Sure, a bit of the romance is lost, but if this becomes available you can bet it will be popular. But these kits are not available at present – the technology is not yet portable and automated enough.

I always like to speculate about how existing technology will advance in the future. The ability to choose the sex of a child by sperm sorting is just the beginning. What if you could go to a lab, or buy a home kit, that would enable you to select from the millions of sperm those that had the genes you desired (not just the chromosome)? At first such technology would likely be used to screen out for genetic diseases. Rather than playing genetic Russian roulette, simply remove the sperm that carry the mutation for that horrible genetic disease.

Once this technology is established (and who can argue against preventing horrible genetic diseases) it is a short trip to selecting for genes that are associated with a lower risk of common diseases. Why pass on that gene for high cholesterol you got from your father, when some of your sperm are carrying the gene from your mother that is associated with low cholesterol? Once the technology works it is likely to progress from preventing genetic diseases to reducing genetic risk for other disease, then to choosing genes that improve biological function (like vision and immune function), and then to height, eye and hair color.

This, of course, is not the same thing as genetic engineering – just genetic sorting. Why leave up to chance which genes you pass onto your children, when you can ensure that you pass on the best of your genes? The genes are still all yours, unaltered. You are not making a super-human, but giving your child the best you have to give. (Can’t you see the ad campaign now?)

Of course, once people are used to the idea of controlling what genes get passed onto their children, it is a short trip to the notion of inserting better genes into the mix. Why deprive your child of that gene that renders people immune to heart disease? It’s not your fault that you don’t have that gene, and why should your children suffer.

You see where this is going. I personally don’t have a problem with any of this, and also recognize that its largely does not matter what I think or anyone else alive today. These changes will come over time, with each generation getting used to the genetic manipulation that is available to them. Those people today who are squeamish about human genetic engineering will likely be considered old-fashioned and naive by later generations. There will also very likely be a subculture of genetic Luddites who refuse any genetic technology, and all power to them. I file this under personal choice and freedom, and argue that one of the fruits of technology is that it grants humans a greater range of choices.

This is why I understand the desire of parents to be able to choose the sex of their children. But this technology (outside of in vitro fertilization) is not yet here, so don’t buy the snake oil.