Choosing your baby’s sex: what the scientists say

Can we choose the sex of our child?

Fertility specialists have the ability to create and identify embryos of either sex. However, it is illegal to choose your baby’s sex in Canada, unless there’s a medical reason for it.

You can only legally choose your baby’s sex in the Canada if you have a serious genetic condition that you risk passing on to your children (HFEA 2009a). So you can’t medically intervene with conception just to “balance” your family, or for social or cultural reasons (HFEA 2009a, HFEA 2012).

There are some cheap, safe techniques that you can try in the privacy of your own home, though they’re pretty unreliable. You could experiment with sex-selection kits or try folklore methods, such as eating more meat if you want a boy!

What would qualify us for sex selection?

You’ll only qualify for pre-implantation genetic diagnosis (PGD) or pre-implantation screening (PGS) if you have a serious genetic disorder such as hemophilia or cystic fibrosis.

PGD reduces the chance of your baby suffering from the same condition, partly by testing for the genes which carry it. PGD is an in vitro fertilization (IVF) technique. At the fertility clinic, embryos are created from your eggs and your partner’s sperm. After these are screened, a specialist will implant two or maybe three embryos in your uterus (womb).

Sex as well as genes can play a part. Duchenne muscular dystrophy, for example, only affects boys. A disease such as hemophilia almost always passes from mom to son. In these circumstances, your doctor would just use a female embryo. He wouldn’t need to test for specific genes as well.

Your clinic will probably offer to freeze any spare embryos. You can then use these if you suffer the distress of a miscarriage, or if you’d like to have more children later on. Using frozen embryos isn’t quite as reliable, but it’s less invasive, and cheaper than another cycle of IVF.

What is sperm sorting?

This is when doctors try to separate male from female sperm. Sperm sorting is illegal in the Canada, but the service is offered, for a considerable fee, in some other countries (HFEA 2009c).

The most-used technique is flow cytometry and is thought to be about 92 per cent accurate for girls, and 82 per cent for boys.

Flow cytometry works by adding a fluorescent dye to your partner’s sperm sample. Experts can then tell male from female by seeing how the dye binds to the genetic material in the sperm.

Once sorted, you can then be implanted with the chosen sperm using relatively cheap intrauterine insemination (IUI).

There’s no guarantee of success with sperm-sorting. And IUI is not as effective as in vitro fertilization (IVF).

Can timing sex decide if we have a girl or a boy?

There are two theories about whether this is possible: the Shettles method and the Whelan method, both named after the person that devised them. Bear in mind that these methods are theories rather than proven techniques.

You may decide to try one method if you understand your cycle well enough. But bear in mind that, whichever method you try, you always have a 50:50 chance of conceiving a baby of the sex you’d like.

The Shettles method
This is based on the idea that male sperm move faster, but don’t live as long as female sperm. So if you want a boy, you should aim to have sex as close as possible to ovulation (Shettles and Rorvik 2006), as the boy sperm will beat the girl sperm in the race to the egg. If you want a girl, you need to have sex two to four days before you ovulate.

Shettles claims that it’s 75 per cent effective for girls and 80 per cent effective for boys (Shettles and Rorvik 2006).

What is the Whelan method?
The Whelan method partly contradicts the Shettles method. It suggests that biochemical changes earlier on in your cycle favour boy-producing sperm. So if you want a boy, you should have sex four to six days before your basal body temperature goes up, or when your OPK says you are about to ovulate. If you want a girl you should have sex two to three days before you ovulate.

There may be more in this, as experts have found that male sperm have an advantage over female sperm at the very beginning and the end of your fertile window (James 2008, Jongbloet 2004). They also suggest that male sperm can survive longer than female sperm (van Dyk et al 2001).

How about sex selection kits?

DIY kits which claim to help with sex selection are based on the Shettles theory. They include instructions, a basal thermometer, ovulation predictor test sticks, supplements, and douches that are supposedly sex specific.

The US manufacturer claims a 96 per cent success rate. But some fertility experts say there’s not enough evidence to back up these claims.