Infertility and ART
Infertility is a frequently common health condition that can be described as the failure of a couple to conceive a child after two years of unprotected sex. Unfortunately, infertility has grown increasingly due to environmental and genetic factors, such as obesity, smoking, alcohol and drug use, as well as environmental pollution (Lal et al., 2020).Therefore, numbers of infertile individuals have quickly risen past 15% of reproductive-age couples (Agarwal et al., 2015). Consequently, assisted reproduction technology (ART), and more particularly during vitro fertilization (IVF) have considered the burden of this increasing demand. These technologies are becoming an increasingly more common means to conceiving a child (Lal et al., 2020).
PGT started as an experimental test in the 1990s using polymerase chain reaction (PCR)-based techniques applied firstly for sex selection and the detection of monogenic disorders. A few years later, Interphase fluorescence in situ hybridisation (FISH) was introduced and became the standard technique for embryos sexing and for identifying numerical and structural chromosomal irregularities (Kokkali et al., 2020). However, PGT-A is usually carried out for in vitro fertilisation (IVF) patients, aiming to increase pregnancy rates per embryo transfer and reducing miscarriage rates. Another benefit of PGT-A is to increase elective single embryo transfer and decreased time to pregnancy. PGT-A milestones also include it application for advanced maternal age (AMA), recurrent implantation failure (RIF) and severe male factor (SMF) and couples with normal karyotypes who have experienced recurrent miscarriage (RM) (Harper et al., 2018).
Three main methods can be performed while doing the TE biopsy: the first start with an opening the zona pellucida at cleavage stage by laser-assisted drilling till the formation of an enlarged blastocyst on day 5. The reason behind drilling the Cleavage embryo zona is to obtain a faster biopsy on an expanded blastocyst and decrease the risk of unexpected collapse. Still, this method has a notable limitation; the embryo will be moved out of the incubators for two times for manipulation, and the substantial risk of having the inner cell mass herniating outside the zona.
The second method is to apply assisted laser hatching for the TE, after the full blastocyst expansion. This approach needs a single embryo intervention, and the zona can be targeted in a range far from the inner cell mass, decreasing its association in the biopsy method. The last approach mixes the previous techniques in which it consists of penetrating the zona when the blastocyst is completely expanded and then waiting for the TE herniation (Greco et al., 2020).
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