For patients with recurrent pregnancy loss

Chromosomal translocation in either partner

• （5）Treatment of antiphospholipid syndrome
• INDEX
• （7）Preimplantation genetic testing for chromosomal structural rearrangement

Forty six chromosomes are found in the nucleus of every human cell. They contain about 22,000 genes and are used to pass on parental traits to the next generation. A translocation occurs when a part of a chromosome is replaced by a part from another chromosome, and we know that 5-8 % of patients with RPL have translocations. There is no excess or deficiency of genes within the chromosome, so it is not an "abnormality" because the person is completely normal and healthy. However, a genetic imbalance occurs only when the ovum and sperm are produced. Patients with a translocation produce both balanced and imbalanced versions of the ovum or sperm. When an ovum or sperm with an imbalance participates in fertilization, the embryo miscarries. Normal eggs and sperm also develop at a constant rate, so a baby can be born to patients with an RPL caused by a translocation.

Table 5: Live birth rates in 1284 coupls with translocation and normal chromoso

For a long time, there was no report on how many miscarriages occur in patients with translocations. We examined the pregnancy outcomes after causal examination in 1284 couples with RPL (Table 5, ref. 16). Fifteen out of 47 couples (31.9 %) with reciprocal translocations were able to complete the first pregnancy after diagnosis. In contrast, 849 (71.7 %) of 1184 chromosomally normal couples gave birth successfully, indicating that couples with balanced reciprocal translocations were more likely to miscarry, although a total of 32 of 47 couples (cumulative live birth rate of 68.1 %) were able to give birth. The Chicago group reported 65% success with the first pregnancy and 90% cumulative success in all pregnancies. A Dutch group reported a cumulative live birth rate of 83% for translocation couples and 84% for chromosomally normal couples, and this group concluded that the prognosis for carriers of translocations was no different from the normal group (17). The Dutch study included a large number of cases and employed excellent research methods and its findings are considered highly reliable.
In our previous study, 7 out of 11 (63.6%) Robertson translocation carriers gave birth in the first pregnancy after diagnosis, which was similar to that in normal couples, and FISH sperm analysis showed that 46.9% of the sperm from reciprocal translocation carriers had normal or balanced alternating segregation. In our study, 88% of patients who were Robertsonian translocation carriers had alternating separations, suggesting that patients with Robertsonian translocations have a higher birth rate than those with reciprocal translocations.
Our 2004 report was based on about 15 years of clinical data and included patients with 10 to 13 previous miscarriages, as well as patients who stopped seeing the doctor after one miscarriage, which is why the birth rate was low. It is important to note that from a global standpoint, miscarriages are relatively uncommon.

Therefore, between 2003 and 2005, a multicenter study (Nagoya City University, Nagoya City Jyosai Hospital, University of Tokyo, Department of Internal Medicine, Osaka Medical Center for Mother and Child, Jikei University, Keio University, National Center for Child Health and Development, Tokai University, Nihon Medical University, and University of Toyama) was conducted (18). Eighty-five of 2382 patients (3.6%) had an translocation and 63% (29/46 pairs) of those with reciprocal translocations were able to give birth in their first pregnancy after diagnosis.

It is not possible to predict how many miscarriages an individual patient will have. This is because the position of the translocated chromosome can make a difference in how much of an imbalance will occur. The inversion of chromosome 9 is a normal mutation and is not associated with miscarriage.
If a chromosomal balanced translocation is found to trigger a miscarriage, the imbalanced child will be miscarried, although 1.6-2.9% of these women may continue to be pregnant (ref. 16, 17).