Sex selection

Human sex selection or gender selection can be accomplished several ways, both pre- and post-implantation of an embryo, as well as at birth. It has been marketed under the title family balancing.

Pre-implantation methods
Two major types of pre-implantation methods can be used for sex selection.

Sperm sorting - The separation of X Chromosome sperm from Y Chromosome sperm. The resulting sorted sperm are used in either artificial insemination or in-vitro fertilization (IVF) procedures.

Preimplantation genetic diagnosis (PGD) - In sex selection cases, embryos resulting from IVF procedures are genetically tested for X or Y Chromosomes. The embryos of the desired sex are then implanted.

Post-implantation methods
Prenatal diagnosis - Amniocentesis and/or ultrasound is used to determine sex of an offspring, leading to subsequent abortion of any offspring of the unwanted sex.

Post-birth methods
Infanticide - The killing, exposing or otherwise disposing of an offspring of the unwanted sex. It is noted that this is not legal in most parts of the world, but is still a common practice in many cultures.

Adoption - The voluntary surrender of offspring of the unwanted sex. Less commonly viewed as a method of sex selection, adoption affords cultures that have a gender preference a legal means of choosing offspring of a particular sex.

Ethical concerns
The application of these techniques to humans creates moral and ethical concerns. Listed here are some of the more common of those concerns:

Sexual discrimination - The idea that if one sex is preferred over another, those individuals in the non-preferred sex would be at a disadvantage. Opponents of sex selection argue that the procedure would artificially unequalize the ratio of females to males, leading to discrimination, potential violence and abuse of the smaller group. Indeed, China has a significant gender imbalance due to the cultural preference of boys and the One Child Policy. There are already many millions more men than women and the problem is likely to get worse. Huge numbers of men with no chance to marry has severe negative social implications such as an increase in rape, prostitution, bride selling, and men being forced into abstinence.

Eugenics - Many fear that PGD, in general, is a 'slippery slope' leading to a society where 'non-selected' individuals would be discriminated against. PGD is used primarily in the U.S. for the purpose of reducing birth defects and abnormalities, but opponents fear that there is nothing stopping persons from using PGD for more eugenic-based purposes.

History and folk beliefs
There are a wide variety of sex selections methods which have not been demonstrated to be effective. Because even implausible and ineffective methods have a "success" rate of 50%, many continued to be recommended by word of mouth.

As early as 330 BC., Aristotle prescribed the ligation (tying off) of the left testicle in men wishing to have boys.

Some people believe that timing conception according to astrological charts can influence a baby's sex, though there is no evidence to support this or any other timing method.