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Xiao Wang and Xiao Li have been married for 4 years and have not been pregnant. They have sought medical treatment from many other hospitals. They have done artificial insemination in 66 in other hospitals and have not succeeded. In 2022, we were introduced by a relative who helped to get pregnant successfully.
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mentioned Infertility always believes that it is a fallopian tube obstruction, ovulation disorder or abnormal semen of the man. "But in fact, genetic factors are also one of the common causes of infertility." Considering that they have unknown primary infertility and do not rule out genetic problems, the doctor advises the couple to perform chromosomal karyotype tests and high-precision clinical exogenous carrier screening in addition to routine examinations. As a result, it was this genetic test that found the major potential for their fertility.
chromosome karyotyping analysis found that the male party had chromosome balanced translocations of and 3 (Figure 1);
high-precision clinical extrinsic carrier screening showed that both spouses carried heterozygous variants of GJB2 deaf gene (Figure 2).
Figure 1. Men's chromosome karyotype report
Figure 2. Couple high-precision clinical extrinsic carrier screening report chromosome balance translocation refers to the breaking of two chromosomes each, exchanged with each other, forming two new derivative chromosomes. Chromosomal balance translocation is the most common chromosomal structural abnormality in humans. The incidence rate is 1%-2% in normal populations, and the incidence rate is significantly higher in infertility and and repeated spontaneous abortions. Because the number of chromosomes in those carrying balanced translocations of is normal, generally without a clinical phenotype, and does not affect normal life. However, 1/18 of the sperm or eggs produced are theoretically carried by translocations of , 1/18 is normal, and 16/18 is abnormal. Abnormal gametes will be eliminated at various stages due to abnormal development, manifested as infertility or repeated fetal abortion in the early stage of pregnancy. The effects of chromosomal abnormalities are generally fatal, while fetuses with single gene abnormalities are often born and become birth defective babies. my country is one of the countries with high incidence of birth defects, with an average of about 900,000 new birth defects each year, of which 40% are caused by genetic factors. Only when the couple is diagnosed with the disease-causing gene before pregnancy can they have the opportunity to block the genetic disease in the first pregnancy. However, some concepts may affect everyone's acceptance of genetic testing:
Concept 1: The couple neither have any phenotype nor a bad birth history, and my child will not have hereditary diseases.
Concept 2: None of our husband and wife’s family has a family history of genetic diseases, and my children will not get genetic diseases.
Concept 3: Prenatal check-up during pregnancy is normal, my child will not get genetic diseases.
In this case, both couples carry GJB2 gene heterozygous mutations. Because the effect of the normal dominant gene can cover up the role of the pathogenic gene and do not occur. This heterozygous , which does not show clinical symptoms but carries the pathogenic gene, is called a carrier, and its pathogenic gene can be transmitted to offspring. When both couples pass on the disease-causing mutation to their offspring, the offspring will become ill. The risk of deafness of the couple is 1/4, and the risk of becoming a carrier of the variant is 1/2.
Figure 3. Genetic characteristics of autosomal recessive inheritance (AR): The couple's phenotype is normal, but they are carriers, and the next generation of 1/4 phenotype is normal, 1/2 carriers, and 1/4 patients. Marriage Examination Prenatal Examination does not include testing of genetic gene . Once a child with a genetic disease is born, it will affect the child's life. Forecasting the risk of offspring in advance is an important measure for preventing hereditary diseases. By detecting the genetic disease pathogenic gene, carriers of pathogenic mutations can be found from people with normal phenotypes, and measures can be taken in advance to avoid the birth of children with a first-time pregnancy genetic disease.
According to their situation, the doctor recommends to perform third-generation test tubes (PGT-SR+PGT-M) to assist pregnancy, and to detect the number, structure and gene mutations of the embryo.A total of 9 blastocyst were obtained in vitro culture. After accurate and complex genetic detection, 6 embryos had abnormal chromosome numbers, and the remaining 3 embryos had normal chromosome numbers. One of them did not carry equilibrium translocations and did not carry GJB2 gene mutations. The couple is preparing to transplant the precious embryo.
The third generation of IVF is officially named pre-embryo implantation genetic detection technology (PGT). Based on the conventional first and second IVF, embryos with morphological availability will be further biopsyed before transplantation, and some cells will be taken for genetic testing, and the embryos that do not occur for transplantation are selected for transplantation, and healthy babies are harvested, blocking the family transmission of genetic diseases from the source of life.
Northwest Women and Children's Hospital Reproductive Center PGT work began in 2009 and was approved in March 2015 to carry out the trial operation of "Pre-implantation Genetic Testing Technology (PGT). In April 2016, the "Embryonic Pre-implantation Heritage Testing Technology (PGT)" was officially launched. It is the first reproductive center in the northwest region to obtain the PGT approval by the National Health Commission of . The center has completed nearly 2,000 cycles of PGT, which can conduct fertility interventions for elderly couples, repeated miscarriage, repeated transplantation failure, severe malformed sperm syndrome, all chromosomal abnormalities, and more than 200 single-gene diseases to help patients to give birth to healthy babies. The current pregnancy rate is about 75%.
Original: Bai Haiyan
Source: Northwest Women and Children Reproductive Center
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