Sex selection is the attempt to control the sex of the offspring to achieve a desired sex. It can be accomplished in several ways, both pre- and post-implantation of an embryo, as well as at childbirth. It has been marketed under the title family balancing. According to the United Nations Population Fund, the reasons behind sex selection are due to three factors and provide an understanding for sex ratio imbalances as well as to project future trends. These factors are: A preference for sons which stems from household structures "in which girls and women have a marginal social, economic and symbolic position, and consequently enjoy fewer rights." These household structures also focus on security in which sons are expected to provide support to their parents throughout their life; Technological growth of prenatal diagnosis which allows parents to know the sex of their unborn child; and Low fertility which increases the need for sex selection by reducing the probability of having a daughter in smaller families. The United Nations Population Fund states that "Local fertility restrictions and spontaneous rapid fertility decline below replacement levels tend to compel parents who want both a son and a small family size to resort to sex selection." Preference for sex of child In many cultures, male offspring are desired in order to inherit property, carry on the family name and to provide support for parents in old age. In countries such as India, China, Indonesia and Nepal sons have been favored over daughters. According to a 2018 Gallup poll, American parents favor boys by a 36% to 28% margin. The results were similar to a survey in 1941, when Americans preferred a boy to a girl by a 38% to 24% margin. The overall preference was driven by men, of whom 43% preferred a son compared to 24% who preferred a daughter. Men's preference for sons was most pronounced among men aged 18 to 29. Women, on the other hand, showed no preference for either sex, with 31% stating that they preferred a girl and 30% responding that they favored a boy. A 2009 study at the University of Ulster found that having sisters, as compared to brothers, can enhance the quality of an adult's life. Cultural son preference There is a preference of parents to have a son over a daughter in many countries. This can be observed through sex ratios of children in