The PGD is  appropiate in couples who already have an affected child with a genetic problem (chromosomal or single gene disorders) and are at high risk of having another one.

P.G.D. should be also considered for couples who have experienced recurrent pregnancy loss due to genetic disorders and couples with unexplained IVF/ICSI failure.

The only requisite is to know if the genetic problem is due to a chromosomal cause or specific mutated genes molecularly characterized. When the disorder is X-linked and the mutation is unknown, the couple could have the benefit of gender selection, transferring only female embryos. There are over 200 disorders that could be prevented by sex selection of embryos.

Additionally, the aneuploidy screening for specific chromosomes prone to disjunction could also be beneficial for women 35 years or older who desire to achieve a higher chance of pregnancy with IVF/ICSI procedures. The rate of embryo aneuploidy mainly increases with the maternal age. The rate of aneuploidy for women 35 years or younger is up to 20%, while at 35-39 years is 20-50% and at 40 years or older is 50% or higher. Several studies have revealed that these rates become worse when the husband has abnormal semen. Other possibility is the entire study of the karyotype at molecular level to assert the normal status of the embryo.

Summarizing, the PGD could be beneficial for carriers of:  

• autosomal or sex linked recessive or dominant mutation.
• balanced chromosome translocations
• dominant mutation with late onset of the condition in a patient who doesn’t want to disclose his abnormal status but wants to be sure of having normal children.
• Familial tumors
• Isimmunization RhD and Kell group
• HLA typing
• Women > 35 y.o. who want to achieve an ongoing  pregnancy.
• Recurrent abortions
• Recurrent IVF failure
• Oligoastenoterathozoospermia

The main advantages of PGD are:

• An increased chance of having a normal baby.
• As the genetic testing is done prior to implantation (preconceptional), it allows avoiding the decision of genetic abortion, unlike conventional prenatal diagnosis.

• Abnormal embryos have a significantly decreased survival rates compared to normal embryos. Therefore there is an increase in the pregnancy rate by not transferring those embryos that have abnormal chromosomes. Abnormal chromosomes in the developing fetus cause approximately 50% of the cases of miscarriages. Therefore, by transferring only normal embryos, the rate of miscarriage is significantly reduced.
• If only normal chromosome embryos are transferred, the pregnancy rate increases and the miscarriage rate decreases. The chance of inducing a pregnancy termination following a CVS or amniocentesis is decreased.
• If PGD becomes widespread, the incidence of many genetic diseases would be reduced.
• Finally, P.G.D. could significantly reduce medical costs with the decrease in medically challenged children being born, but mainly avoid the emotional stress that the handicapped children cause.
• Because PGD is not yet 100% accurate (90-95%), it is recommended that chorionic villi sampling CVS or amniocentesis are performed for confirmation of normal genetic constitution.