How clinics ‘guarantee’ a girl or a boy

TO choose the sex of a child, IVF couples must provide eggs and sperm to make a baby in the lab.

It is possible to pick a male or female embryo by removing just one or two cells after around five days and checking their X and Y chromosomes.

Girls have XX chromosomes, while boys have XY. Then the correct embryo is put into a woman to make her pregnant.

Some clinics claim the method guarantees the sex of a child with 99 or even 100 per cent accuracy. Other sex selection techniques include sperm sorting, which uses dye to make X chromosome-carrying sperm glow more brightly – because it contains more DNA – and separates the X and Y sperm from each other.

But this method of choosing ‘girl’ or ‘boy’ sperm is used less often and is seen as less effective.

Pre-implantation genetic diagnosis (PGD) can be used to check for hereditary sex-linked diseases like haemophilia and Duchenne muscular dystrophy, which mainly affect boys.

While laboratories in the UK can find out the sex of embryos created using IVF, this is not told to couples or even their doctors.

Other less scientific methods of gender selection are available, with some people swearing by diets and certain sexual positions.

Experts have claimed that men who scuba dive and cycle can damage delicate Y chromosome sperm so are more likely to have girls.