When you're pregnant, one of the most common questions that people ask is whether you know what you're having. Presumably because it's one of the few characteristics you can know about your child while it's still cooking.
Some parents don't mind - the old 'as long as it's healthy' sentiment. But, whether they admit it or not, some people have a strong preference for one gender or the other, and are willing to do anything it takes to get a little girl or a little boy.
If you want an insight into a person's mind, looking at their search history is the way to do it. Looking at thesearch terms for sex selective conception is fascinating. In the UK, Australia, Ireland and Philippines between 50 - 60% of people search for 'how to conceive a girl'.
In the USA and Canada the trend is inverted, with around 10% more people looking to conceive boy babies.
In Kenya 64% of people who searched for sex selective conception were looking for a boy, in South Africa it's 64% and Nigeria it's 76%.
Time was where it was just old wives tales that couples with a strong gender preference tried out. Eating certain foods, drinking certain drinks - all very unscientific.
But research into how conception works has shown that when you have sex in relation to ovulation does have a provable relationship with the gender of your baby. Male sperms - XY - are lighter and faster. Female sperm - XX - are slower but hardier and live longer.
Therefore if you have sex closer to ovulation you are marginally more likely to conceive a boy, and if you have sex later you're a bit more likely to have a girl.
Of course it's not an exact science, and for people who really want a guaranteed outcome, it's not enough.
Scientists in Japan are have created a process which can separate out the male sperm and female sperm, meaning that women could be inseminated with a sperm that has a fixed sex outcome.
The process was discovered when the researches found that sperm bearing the X chromosome, which generates female offspring, carries molecules which when activated slow its movement. When a chemical to trigger those receptors is added, male Y chromosomes power ahead, separating themselves from the slower Xs.
Currently the idea is that it will be used in farming to create more female animals and fewer males, which would mean less sex selective animal slaughter.
Sex selective IVF is currently not legal in the UK, however it is legal in Cyprus and in the USA.
Concerns have been raised about the ethics of sex selective IVF in humans, acknowledging that if it became standardized, cultures where one sex is favoured over another will end up with an imbalanced gender birth rate.
However, defendants of the practice have said that sex selective IVF would put an end to sex selective abortions, and that people undergoing IVF should be entitled to control over their own genetic matter.