<unk>  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<unk>  are due to three factors and provide an understanding for sex ratio imbalances as well as to project future trends. The 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<unk>  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<unk> .”
Sex selection
Cancer selection
Structural inheritance
Sexual reproduction
Dynamic mutation
Nuclear sexing
Immune privilege
Genomic imprinting