The main purpose of this study was to compare the embryo development and pregnancy outcome in different sex in chromosomal translocation carriers (including reciprocal translocation carriers and Robertsonian translocation carriers) undergoing PGT-SR. We found by comparison that the fertilization rate of female carriers was higher than that of male carriers but the blastocyst formation rate was lower than that of male carriers. This seems to indicate that male genetic material plays an important role in the process of fertilization, and that the normal development of an embryo may be more dependent on female genetic material. Embryo chromosomes are derived from both parents. During meiosis, two translocation chromosomes and two homologous normal chromosomes form tetravalent chromosomes and separate at anaphase. Normal or balanced gametes are produced by means of alternate separation, and gametes produced by other patterns of separation have unbalanced karyotypes . Studies have suggested that the difference in carrier sex affects the separation pattern of meiosis of tetravalent genes . There are many factors that affect the separation pattern of meiotic chromosome, including carrier sex, maternal age, translocation chromosome type and translocation segment length, etc . Therefore, we divided patients in reciprocal translocation group and Robertsonian translocation group respectively into male carriers and female carriers, and compared the influence of carrier sex on embryo development and pregnancy outcome in the same type of translocation with no difference in maternal age. In the reciprocal translocation group, the blastocyst formation rate in female carriers was lower than that in male carriers, but biopsy results and pregnancy outcome were not statistically different between the two. Female gametes are more prone to meiosis chromosome errors than male gametes . This was not reflected in the biopsy results of the reciprocal translocation carriers in this study but in the blastocyst formation rate, indicating that some embryos that did not develop properly due to chromosomal abnormalities have been eliminated during embryonic development. In the Robertsonian translocation group, the fertilization rate of female carriers was higher than that of male carriers but the normal rate of biopsy was lower than that of male carriers, and the pregnancy outcome was still not statistically different. This result is comparable to the research of Li Xinyuan et al . According to Munne, the meiotic segregation pattern of female carriers of Robertsonian translocation is different from that of male carriers, and the rate of producing unbalanced gametes is higher than that of male carriers , which is consistent with our results. However, most studies have shown that regardless of the sex of the Robertsonian translocation carrier, alternate separation is the main mode of embryo separation . In addition, many studies at home and abroad have shown that there is no difference in pregnancy outcome of PGT-SR between male and female carriers of chromosomal translocation , and our research have also come to the same conclusion.
At present, PGT has become a basic and important choice of assisted reproductive technology for patients with chromosomal translocation. With the continuous development and improvement of technology, more and more chromosome detection methods are applied in PGT. Fluorescence in situ hybridization (FISH), previously widely used, can only assess a discrete number of chromosomes, usually 9–12 at a time . However, data from the evaluation of 23 pairs of chromosomes of embryonic DNA have shown that aneuploidy is relatively evenly distributed in all 23 chromosomes . Therefore, FISH technology is at a significant disadvantage in the identification of aneuploidy. In this study, SNP or NGS methods were used in all cycles, which are currently more extensive method of diagnosing embryonic chromosomal abnormalities  and all 23 pairs of chromosomes can be comprehensively screened. It has obvious advantages compared with FISH technology, which can only detect a limited number of chromosomes . In addition, compared with previous biopsy at cleavage stage, blastocyst trophoblast cell biopsy can not only control the damage of biopsy to embryos, but also ensure the accuracy of sequencing results .
A successful clinical pregnancy depends on many factors, such as maternal age, cause of infertility, infertility duration, endometrial receptivity, etc but only if there is a normally developing transplantable embryo. Based on a large number of PGT-SR cycles, we did a retrospective analysis and explored the effects of carriers of different sex on embryonic development and clinical pregnancy outcomes in reciprocal translocation and Robertsonian translocation, providing ideas for in-depth understanding with the process of embryonic chromosomal abnormalities. At the same time, it also provides clinical evidence for the application of PGT assisted fertility treatment. However, our study also had several limitations due to its retrospective design and a single medical center, and there is an inevitable bias. In addition, this research is only a preliminary discussion and the conclusions needed to be interpreted carefully.