The desire to have a child of a certain sex has existed since ancient times. Superstitions about determining the sex of a child during intercourse are part of Western folk tradi – tion—for example, the belief that if a man wore a hat during intercourse, he would father a male child or that if a man hung his trousers on the left bedpost, he would sire a girl.

Couples sometimes try "low-tech" methods to conceive a boy or girl. Timing inter­course closer to ovulation (to conceive a boy) or further from ovulation (to conceive a girl), making the vaginal environment more acidic or alkaline by douching with water and vinegar (girl) or water and baking soda (boy), or using different intercourse posi­tions such as man on top (girl) or rear-entry (boy) are among the techniques that couples may try. However, there is no scientific consensus as to whether any of these methods are effective.

An effective technique for sex selection, pre-implantation genetic diagnosis (PGD), creates embryos in the laboratory. The sex of the embryos is tested, and a physician sub­sequently inserts the embryos of the desired sex into the woman’s uterus. The approx­imately $20,000 procedure offers almost 100% certainty of the baby’s sex (Dayal & Zarek, 2008). Less certain results occur with more commonly used laboratory tech­niques that can separate X-chromosome-bearing sperm from Y-chromosome-bearing sperm. Once the laboratory separation process is complete, the desired X or Y portion is introduced into the vagina by artificial insemination. Success rates are about 90% for female babies and 70% for male babies. However, the rather "unromantic" nature of semen collection and artificial insemination will probably limit the use of sex selection techniques unless parents have compelling reasons to conceive a child of a particular sex.

Sex preselection offers benefits to couples at risk for passing on X-chromosome-linked diseases to their children, and research indicates that the public strongly favors its use for that purpose (Kalfoglou et al., 2008).

In China, India, and South Korea, the preference for a son is particularly strong, and selective abortion of female fetuses and the killing of infant girls are common. In India a woman can obtain an ultrasound for about $12 to determine the sex of the fetus, and if it is a girl have an abortion for about $35 (Power, 2006). Consequently, an imbalance in the numbers of boys and girls has occurred: For every 100 girls there are 120 boys in China and 109 in India. The imbalance is most severe in wealthier regions where couples can afford the ultrasound tests (Halarnkar, 2011; Hvisten – dahl, 2011). Overall, there are currently 100 million more males than females in Asia (Ferguson, 2011).

Economic and cultural factors contribute to the importance of sons in many Asian cultures. Sons provide for parents through their old age, offering security in the absence of governmental social support. In Hindu and Confucian religious traditions in Asia, only sons can light their parents’ funeral pyres and pray to release the souls of dead parents. Sons will bring future earnings to their parents, but daughters are a financial liability to their families when they require the expense of a dowry. Women’s work will also contribute to the family into which they marry instead of to their birth family (Garlough, 2008). These traditions are so strong that even Asian couples who have immigrated to the United States are using medical technology to have sons instead of daughters. Interviews with immigrant Indian women who pursued fetal sex selection found that 40% of the women had terminated prior pregnancies with female fetuses and that 89% of women carrying female fetuses in their current pregnancy pursued an abortion (Puri et al., 2011).