What is Big Y

Patient's question:

Dead fetus after being pregnant for three and a half months

Doctor's answer:

Here is the English translation of the provided text, with line breaks () preserved as instructed:
?1 The association between a large Y chromosome and unexplained early pregnancy miscarriage, embryonic arrest, stillbirth, and other adverse pregnancy outcomes is the most common case seen in genetic counseling clinics. Whether a large Y can cause embryonic developmental abnormalities, miscarriage, and increase the risk of miscarriage remains a controversial topic. Most domestic scholars believe that a large Y is a normal variation. For example, Li Yi [1] stated that the incidence of a large Y in the normal population is 13%–17%, while in chromosomal examinations of 447 couples with fetal loss during the same period, the incidence of a large Y accounted for 13% of the total tested cases, showing no significant difference. This suggests no clinical significance and that it may be unrelated to adverse pregnancy history. However, recent reports have increasingly indicated that a large Y has a genetic effect and is associated with pregnancy and fetal loss. In the study by Huang Guomei [2], 16 out of 29 cases with a large Y (55.1%) were associated with recurrent miscarriages in their wives, which is close to the findings of this study. Foreign studies have shown that the frequency of a large Y in couples with miscarriage is 19.6%, and it is believed to increase the risk of miscarriage. Among the 145 cases with a large Y in this study, 80 cases (55.17%) involved recurrent miscarriages in their wives. One case involved a large Y male whose wife gave birth to a child with hypospadias (the child’s chromosomes were also found to be large Y), followed by three consecutive spontaneous miscarriages. The reason for how a large Y causes embryonic developmental abnormalities and miscarriage is usually explained as being related to excessive DNA repeats in the Y chromatin. With the rapid advancement of molecular biology techniques and the implementation of the Human Genome Project, if the structure and function of the Y chromosome can be studied at the genetic level, the cause of pregnancy and fetal loss associated with a large Y will be further confirmed. [3] 2 Large Y and Developmental Abnormalities In this study, developmental abnormalities mainly included growth retardation and urogenital tract malformations, accounting for 21 cases (14.48%). Among these, 4 cases involved large Y males whose partners had previously given birth to children with Down syndrome. Three cases involved dwarfism combined with a large Y, one case involved conjoined twins, two cases involved intellectual disability, and six cases involved hypospadias, all in large Y males. Previous reports have suggested that a large Y can lead to male testicular dysgenesis, sexual development abnormalities, and hypospadias [3]. This study’s results also support these conclusions. Whether a large Y is associated with intellectual disability remains uncertain, as factors leading to intellectual disability include both genetic and environmental factors, such as Down syndrome, where an extra 21 chromosome results in intellectual disability. It can be inferred that the expression and regulation of human intelligence genes may be related to chromosome 21. However, the role of the Y chromosome is still unclear, and whether a large Y causes intellectual disability requires more research for evidence. [3] 3 Large Y and Adverse Early Pregnancy Exposure History The use of teratogenic drugs during early pregnancy or concurrent TORCH infections are significant factors that can induce gene mutations leading to fetal malformations. In this study, among 124 cases requiring umbilical cord blood sampling for prenatal diagnosis due to early pregnancy medication use and TORCH infections, 16 cases involved large Y male fetuses, with an incidence as high as 11.03%. Family history investigations revealed normal karyotypes in all fathers, suggesting that adverse early pregnancy exposure history can increase the incidence of Y chromosomal abnormalities. The possible mechanism is as follows: cells exposed to toxic substances or viral infections during early pregnancy may induce DNA mutations [4].? In light of the above discussion, genetic counseling should be provided to patients and their families by consulting doctors in clinical prenatal diagnosis. For example, we previously found that 4 cases of large Y males had a history of giving birth to children with Down syndrome, suggesting an increased likelihood of having offspring with chromosomal abnormalities. The use of teratogenic drugs during early pregnancy and viral infections may lead to fetal chromosomal abnormalities, and amniotic fluid or umbilical cord blood should be sampled for chromosomal testing at appropriate times. Hypospadias patients often have a large Y, and the incidence of intrauterine hypoxia and preterm birth in large Y fetuses is higher. Therefore, chromosomal testing is necessary for premature infants. These are achievable in clinical practice and are of great significance for improving the quality of the birth population and promoting eugenics.