Establishment of a pregnancy of a female fetus could also be achieved if sperm could be separated into X- and Y-bearing populations. There have been publications reporting on the use of various methods to separate X or Y chromosome-bearing sperm (Ericsson, 1994; Vidal et al., 1993). The initial aim of these methods was to select the sex of the fetus for social reasons (see below) for couples that already had several children of one sex (Chapter 14; p. 258). However, if an efficient method could be found for separating X-bearing sperm, this could be used for inseminating women at risk of transmitting X-linked disease. Techniques using albumin gradients were reported to separate either X- or Y-bearing sperm, depending on the exact method used (Ericsson, 1994) and methods using Percoll and Sephadex gradients were tried (Vidal et al., 1993). Unfortunately, using FISH to confirm the ratio of male and female sperm in samples prepared by these methods, it has been shown that there is no significant difference in the numbers of X- or Y-bearing sperm (Vidal et al., 1993; Flaherty & Matthews, 1996). More recently, the use of the Hoeschst dye 33342, or bisbenzimide, in conjunction with flow cytometry, has reported the separation of X- and Y-bearing sperm, with a purity of 85% for X-bearing sperm and 65% for Y-bearing sperm (Vidal et al., 1998). However, there are some concerns as bisbenzimide and UV irradiation could cause mutation and chromosome damage. Using this method, only small numbers of sperm are retrieved and often this has to be used in conjunction with ICSI to obtain fertilization.
However, recently a number of pregnancies have been established using intrauterine insemination of flow sorted sperm (Fugger et al., 1998).
Sexing of embryos for family balancing has already been offered in at least two centres (ESHRE PGD Consortium meeting, June 2000). The use of PGD for nonessential characteristics is controversial (see Chapter 14; p. 258). In the UK sexing embryos for family balancing has been banned by the Human Fertilization and Embryology Authority. Some groups feel that once PGD is offered for certain characteristics such as sex rather than a genetic disease, then we are on our way to the use of PGD for non-medical reasons (see Chapter 14; p. 258). This has been discussed elsewhere (Ethics Committee of the American Society of Reproductive Medicine, 1999).
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Whenever a doctor informs the parents that their child is suffering with Autism, the first & foremost question that is thrown over him is - How did it happen? How did my child get this disease? Well, there is no definite answer to what are the exact causes of Autism.