<unk>  undergoes a process of natural selection when millions of<unk>  enter the vagina but only few reach the egg cell and then only one is usually allowed to fertilize it. The<unk>  is selected not only by its highest motility but also by other factors such as DNA integrity, production of reactive oxygen species and viability. This selection is largely circumvented in case of in-vitro fertilization which leads to higher incidence of birth defects associated with assisted reproductive techniques. Egg cells are often fertilized by<unk>  which would have low chance of fertilizing it in natural conditions.<unk>  could thus be used to decrease risks associated with assisted reproduction. Additionally, there is ongoing debate about using<unk>  for choosing the child's sex. For general health Conventional methods of<unk>  have been widely used to assess quality of<unk>  before subsequent artificial insemination or in-vitro fertilization. It has been verified that<unk>  sorted using these techniques is of superior quality than unsorted. However, important characteristics of<unk>  such as DNA integrity remain untested by these conventional methods. New flow-cytometry based techniques such as YO-PRO staining can discriminate apoptotic and dead<unk> atozoa from the viable ones. For example, annexin V staining followed by MACS can significantly improve pregnancy rates in couples with previous assisted reproduction failure. For sex selection In farming<unk>  by flow cytometry is an established technique in veterinary practice, and in the dairy industry most female cows are artificially inseminated with sorted semen to increase the number of female calves (using<unk>  is less common in other species of farm animals, however artificial insemination is common). Artificial insemination of farm animals with sorted<unk>  is recognized by the Food and Agriculture Organization (FAO) as a promising way of increasing efficiency of agriculture needed to produce enough food for the growing human population. Utilizing artificial insemination with sorted<unk>  is seen as a way to create an optimal ratio of male and female calves to increase dairy milk production. In humans Choosing the sex of children might help prevent sex-associated heritable diseases such as Duchene muscular dystrophy or haemophilia in families with a history of these diseases. On the other hand,<unk>  in humans raises the ethical concerns implicit to the idea of sex selection. If applied large-scale, it has a potential to elicit a sex-ratio imbalance. It could also have implications on gender equality if parents consistently choose to have a boy as their first-born (first-borns were shown to be more likely to succeed in life). There is no country in the world which explicitly<unk> its sex selection for non-medical purposes. There were 31 countries in 2009 which allowed sex selection in case of sex-linked disease risk or other medical purpose. In the US, for humans, the application of<unk>  in sex selection is tightly regulated by the FDA. After the establishment of the MicroSort technique, it was offered to parents as a part of a clinical trial. The procedure was made available to a limited number of participants each month, in addition to fulfilling certain criteria, such as having a disease with sex linkage or having at least one child (for family balancing). There are currently MicroSort laboratories and collaborating physicians in several countries (some for general purposes, some only offering service in case of genetic disease risks associated with one sex). While highly accurate,<unk>  by flow cytometry will not produce two completely separate populations. That is to say, there will always be some "male"<unk>  among the "female"<unk>  and vice versa. The exact percentage purity of each population is dependent on the species being sorted and the 'gates' which the operator places around the total population visible to the machine. In general, the larger the DNA difference between the X and Y chromosome of a species, the easier it is to produce a highly pure population. In sheep and cattle, purities for each sex will usually remain above 90% depending on 'gating', while for humans these may be reduced to 90% for "female"<unk> atozoa and 70% for "male"<unk> atozoa.
Sperm sorting
Postcoital test
Fertility testing
Cytogenetics
Semen collection
Karyotype
Triple smear
Magnetogenetics