In medicine and (clinical) genetics preimplantation genetic diagnosis (PGD) is a method to test embryos for genetic disorders before they are reimplanted in the uterus.
When a genetic disorder occurs in a family, the parents are usually reluctant to attempt pregnancy again, given the 25-50% chance (dependent on the type of disorder) of recurrence after a previous child has been affected.
A solution to the problem is the use of in vitro fertilisation (IVF) with testing of each embryo at blastocyst stage for the presence of the disease-causing genes. Although there remains a small chance of false negative results, this would eradicate the possibility of recurrence of the disease in question.
In theory, PGD could be used for sex selection, a very controversial procedure to ensure that offspring is of one particular sex, or selection on the presence or absence of other genetically determined traits.
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