BEIJING, Dec. 23 (Xinhua) -- Every couple of childbearing age looks forward to having a healthy baby, but in China, the total incidence of birth defects is about 5.6%. Among the various causes of birth defects, single-gene genetic diseases account for about 22.2%. In routine obstetric examinations, children with recessive genetic disorders are usually unable to detect abnormalities until after birth. How to check the risk of children with recessive genetic diseases in a timely manner?
Without a family genetic history, children will also get sick?
According to data revealed by the National Health Commission in 2018, it is estimated that the total incidence of birth defects in China is about 5.6%.
Studies have shown that on average, each normal person carries 2.8 disease-causing variant genes for recessive genetic diseases, which can be inherited from both parents and themselves, and may be passed on to the next generation.
Hao Na, a technician in charge of the Obstetrics Center of Peking Union Medical College Hospital, introduced that single-gene genetic diseases refer to genetic diseases controlled by a pair of alleles, with more than 9,000 species, such as progressive pseudo-hypertrophic muscular dystrophy, spinal muscular dystrophy, thalassemia, phenylketonuria, etc.
The combined incidence of single-gene disease in the population is one percent, and the genetic pattern of single-gene recessive disease is as follows:
Courtesy of obstetrics center of Peking Union Medical College Hospital.
Hao Na introduced that when the human body carries a mutated gene of a single-gene recessive genetic disease, it is called a carrier. Carriers themselves do not develop the disease, but there is a 50% chance that the mutated gene will be passed on to the child.
When both husband and wife are carriers of the same single-gene recessive genetic disease, and the fetus inherits the couple's respective defective genes at the same time, it will become sick in the future and become a patient. The probability of such a couple giving birth to a child with this genetic disorder is 25% per pregnancy, and the probability of having an asymptomatic carrier is 50%.
In addition, when the woman is a carrier of the causative gene of X-linked recessive genetic disease, there is a 50% probability that the boys who give birth to each pregnancy are children, and 50% of the girls who give birth are carriers.
Early screening and testing is significant
Single-gene genetic disorders can be extremely burdensome and traumatic to both patients and their families.
Doctors say that most single-gene genetic diseases are fatal, severely teratogenic or disabling, and there is a lack of targeted treatments and therapeutic drugs (only about 5%), which is expensive and usually only symptomatic or rehabilitation.
Therefore, for expectant parents, it is of great significance to carry out effective risk assessment and diagnosis and identification of common single-gene genetic diseases during pregnancy preparation or early pregnancy.
Expectant parents can screen carriers by blood tests during pregnancy or in the first trimester to detect high-incidence single-gene genetic diseases and check for pathogenic genetic mutations.
Jiang Yulin, deputy chief physician of the Obstetrics Center of Peking Union Medical College Hospital, suggested that patients with high suspicion of single-gene genetic diseases, couples with a family history of hereditary diseases or children with genetic diseases need to first conduct genetic diagnosis and screening for the causes of their own diseases or family history, and then the doctors will recommend whether it is suitable for screening single-gene disease carriers.
If the test finds that the couple is also a carrier of a single genetic disease, it is necessary to combine genetic counseling, prenatal testing or diagnosis, assisted reproductive technology, etc., to effectively prevent serious single genetic diseases in the fetus.
Data map: A hospital outpatient building. China News Service reporter Yin Liqin photographed
Pregnancy preparation is the best time for screening
Hao Na said that the best time to carry out screening for single-gene genetic disease carriers is the pregnancy preparation period, during this period, expectant parents have more time, so the consideration and decision-making of the test results are relatively calm, and there are more alternative solutions.
If you miss the pregnancy preparation period, don't worry, screening in the first trimester is also OK, but in this period of testing, the time is more tight, so it is recommended that both husband and wife at the same time to draw blood tests.
Single-gene genetic disease carrier screening is simple and fast, expectant parents first in the outpatient clinic after professional consultation, and sign the relevant informed consent, the couple for blood draw (3 to 5 ml of peripheral blood) test, generally 3 to 4 weeks can produce results.
Therefore, couples of childbearing age who have fertility intentions can screen single-gene recessive genetic disease carriers during pregnancy preparation or in the first trimester to understand their own mutant gene carriers, early detection of fertility risks and timely intervention, which can effectively prevent the occurrence of serious genetic diseases. (End)
Source: China News Network