Reprogenetics: preimplantational genetics diagnosis

Abstract

Preimplantational Genetics Diagnosis (PGD) is requested by geneticists and reproductive specialists. Usually geneticists ask for PGD because one or both members of the couple have an increased genetic risk for having an affected offspring. On the other hand, reproductive specialists ask for embryo aneuploidy screening (PGS) to assures an euploid embryo transfer, with the purpose to achieve an ongoing pregnancy, although the couple have normal karyotypes. As embryonic aneuploidies are responsible for pre and post implantation abortions, it is logical to considerer that the screening of the embryonic aneuploidies prior to embryo transfer could improve the efficiency of the in vitro fertilization procedures. Nevertheless, it is still premature to affirm this until well-designed clinical trials were done, especially in women of advanced age where the rate of embryos with aneuploidies is much greater. Although the indications of PGD are similar to conventional prenatal diagnosis (PND), PGD has less ethical objections than the PND. As with the PGD/PGS results only unaffected embryos are transferred, both methods can avoid the decision to interrupt the pregnancy due to a genetic problem; this makes an important difference when compared to conventional prenatal diagnosis.

Genetic Considerations in Recurrent Pregnancy Loss

“…Although removing a second blastomere at the time of sampling may improve accuracy, this comes at the cost of decreases in embryo survival (Harper et al 1995;Delhanty 1997;Munné et al 1999;De Vos et al 2009;Harton et al 2011). A significant disadvantage of cleavage stage blastomere biopsy is the associated decrease in implantation rates for biopsied embryos (Coco 2014). A final drawback of both polar body and blastomere biopsies is the paucity of collected materials, typically only a single cell or its equivalent.…”

“…Trophectoderm biopsy at the blastocyst stage is rapidly becoming the most common sampling modality for PGD and PGS. One advantage of trophectoderm biopsy over cleavage stage biopsy is its ability to improve genetic screening accuracy by safely sampling a greater number of cells per biopsy (Yang et al 2012b;Coco 2014). Because only extraembryonic material is sampled (similar to sampling of a chorionic villus later in the first trimester of pregnancy), a further advantage is a reduced risk of harm to the future fetus.…”

A rare case of in vitro fertilization: Patau syndrome associated with bilateral anophthalmia

“…The rate of aneuploid oocytes increases with advancing age and it is often increased in males with oligoasthenoteratozoospermia. 6 PGD testing is indicated in couples with recurrent miscarriages, couples with repeated IVF failures, severe male infertility, and mothers with increased age. 6 High costs make these tests optional (to select a single euploid embryo for transfer, or to decrease the transmission of genetic disorders to the offspring, or for sex selection).…”

“…6 PGD testing is indicated in couples with recurrent miscarriages, couples with repeated IVF failures, severe male infertility, and mothers with increased age. 6 High costs make these tests optional (to select a single euploid embryo for transfer, or to decrease the transmission of genetic disorders to the offspring, or for sex selection). 6 The timing and technique used for biopsy, the amplification techniques, the genetic diagnosis techniques, and appropriate genetic counseling play important roles in establishing a successful PGD.…”

Current methods for preimplantation genetic diagnosis

“…Using this method, by 2004 approximately 1,000 children had been born [2], and by 2010 this number had exceeded 10,000 [3,4]. Initially, the procedure was thought to be extremely complicated and associated with a high risk of error.…”