Sex selection is considered for one of three reasons:
1. Avoiding sex related genetic disorders. These are genes mostly carried on the X chromosomes and affect boys more than girls since they have one X chromosome e.g hemophilia
2. Family balancing: couples that have children of one sex and desire a child of the opposite sex
3. Preference: some prefer a child of certain sex due to social factors. Recent poll in The UK indicates that when 2,129 recently married couples were surveyed, found that 47% admitted that they would prefer to have a son first, with the majority citing practical reasons like boys being “less hard work”. Only 21% of respondents said they would like to have a daughter as their firstborn, and 32% reported having no preference either way. Couples who wanted to have a daughter first see older girls as ‘better role models’ to their younger siblings. In the US a Gallup poll yielded similar answers by American parents, especially men, since 1940s. American women do not have a proportionate preference for girls. American women show essentially no preference either way: 31% say they would prefer a boy and 33% would prefer a girl. More recent trends indicates that American couples prefer girls.
In contrast couples on a waiting list for adoption prefer girls both in the US and India. There is also some evidence that sexual orientation may influence that preference. Gay men are more likely to have a gender preference for their adopted child whereas heterosexual men are the least likely. Couples in heterosexual relationships are more likely to prefer girls than people in same-gender relationships.
The preference is also influenced by geography and politics. The official family planning policy in China, applied to large portions of Chinese, allow only for one child and does not allow sex selection. In the US many couples desire to limit the number of children to 2. If the first child is of one sex they desire the second child to be of the opposite sex
How is the sex of the embryo determined?
Older methods of selecting sex through change in the position or timing of intercourse or sperm sorting are not accurate and are not suitable for sex selection in modern couples seeking a specific sex (the other sex maybe conceived in 30% or more of couples). Modern sex selection depends on genetics. After stimulation of the ovaries, egg retrieval and fertilization, one or few cells from the embryo is obtained. The cells are analysed for each embryo for the X and Y chromosome. Results are obtained and are accurate >99% of the time.
After identification of the X and Y chromosomes, the desired embryo is transferred into the uterus. The embryo that carries the correct chromosome, should survive and be of good quality. Sex selection is more likely to succeed in women with good ovarian reserve, producing a good number of eggs. The larger the number of embryos available for testing, the more likely a healthy embryo of the desired sex is available for transfer.
Learn more about gender selection.Sex Selection by Dr. Amr Azim