In our obstetrics and gynecology, there is such a metaphor - the process of each life coming to the world is a process of fighting monsters, successful conception is the first level, escaping various accidental miscarriages is the second level, and hiding birth defects is the third level. In fact, most "expectant parents" think that crossing the first two levels is too peaceful, and underestimating the difficulties of the third level. With the implementation of the national policy of encouraging fertility, the growth of elderly women will be more and more stuck in the third hurdle.
First of all, we need to know what birth defects are. As the name suggests, birth defects refer to the abnormalities of the body structure, function or metabolism of the baby before birth, that is, in the mother's body, which is often referred to as "congenital malformations". About 5 million babies with birth defects are born worldwide each year, with an incidence of between 3 and 4 percent. According to the "China Birth Defect Prevention and Control Report (2012)", the total incidence of birth defects in mainland China is about 5.6%, which is a typical high incidence country.
Not all birth defects have serious consequences, and there are different types of them. Clinically, we divide birth defects into two categories: structural defects and genetic defects. Like the small flesh near the ear and the six fingers, it belongs to the appearance and morphological defects in the structural defects, although also called birth defects, but it is very mild, and it does not have much impact on the healthy growth of the baby, including later working life in society.
The biggest impact is the structural abnormalities of the organs in the structural defects, such as congenital heart disease, neural tube malformations, and almost all genetic defects. Because genetic defects mostly involve chromosomal abnormalities, it is a problem with the underlying code of life, which triggers systemic risks. For example, Down syndrome, which is caused by an extra chromosome 21 in the human body, is manifested as intellectual disability and multiple malformations, and there is no effective treatment at present. There is also congenital deafness, at present, in every 1,000 newborns in the mainland, about 1-3 have hearing impairment, of which hereditary deafness accounts for a large proportion.
Overall, at a high incidence of 5%, mild birth defects account for a large proportion. Due to the advancement and abundance of prenatal screening methods, the incidence of severe birth defects is about 1%. Of course, we can't underestimate the 1%, because for any 1% of the family, they are suffering 100%.
Once we have a basic understanding of birth defects, we can explore the reasons behind them. It is generally believed that there are several known culprits. One is genetic factors, in layman's terms, that is, at least one of the parents carries a mutated gene. Most of this condition is recessive inheritance, that is, the parents carry a certain gene but do not develop the disease, but inherit it to the offspring. The second is maternal factors, such as maternal infection, taking drugs during pregnancy, smoking and drinking, insufficient nutritional supplementation and so on. The third is environmental factors, such as electromagnetic radiation pollution, radioactivity, high temperature and high heat, and even the most common air and noise pollution in life.
These factors can appear independently or work together. But whatever the cause, the vast majority of birth defects can be avoided by preventive measures.
Now universally accepted is the tertiary prevention strategy for birth defects proposed by the World Health Organization. Primary prevention refers to comprehensive intervention before pregnancy and in the first trimester of pregnancy, through health education, selection of the best reproductive age, genetic counseling, regular health care, reasonable nutrition, no exposure to radioactive or toxic and harmful substances, prevention of infection, prudent use of drugs, smoking and alcohol cessation, etc., to reduce the occurrence of birth defects; secondary prevention refers to the identification of serious birth defects of the fetus through screening during pregnancy and prenatal diagnosis, early detection and early diagnosis to reduce the birth of children with defects; tertiary prevention refers to early screening and early diagnosis of neonatal diseases 3. Timely treatment to avoid or reduce the disability of newborns and improve the quality of life of children.
Relatively speaking, secondary prevention is the core link in the whole set of strategies, and the focus is on two words - obstetric examination. For the fetus, the most important thing in obstetric examination is the screening and diagnosis of birth defects, which includes the chromosomal abnormalities of the fetus and the structural abnormalities of various organs and systems of the fetus. For pregnant women, the three most important screening and diagnosis of fetal birth defects are: NT + non-invasive prenatal genetic testing + large diastelia, which is a high proportion of obstetric examination, and it is best to do it if there is a condition.
Let's first look at NT, which is an abbreviation for Nugual Translucency, which refers to the thickness of the transparent layer of the fetal neck at 11-14 weeks of pregnancy in the first trimester. This ultrasonography may seem simple, but it is very useful. NT is an ultrasound soft marker that can often be found in the fetus during pregnancy ultrasound, and the ultrasound soft marker is not a fetal structural abnormality, but its appearance will indicate an increased risk of chromosomal and organ structural abnormalities in the fetus. The greater the thickness of NT, the higher the risk of fetal chromosomal abnormalities, fetal heart malformations, and stillbirth.
There was once a hospital in China that conducted a retrospective survey and analysis of 7153 women between 2015 and 2020, and the 7153 cases of prenatal fetal malformation screening confirmed 143 cases of malformed fetuses through induction of labor or delivery follow-up results, and 136 cases were detected by ultrasound, with a detection rate of more than 95%, which is enough to prove the importance of prenatal ultrasound.
Non-invasive prenatal genetic testing, which can be detected at 12 weeks of pregnancy, is the application of molecular genetic techniques such as high-throughput gene sequencing to detect free DNA fragments of the fetus in the peripheral blood of the mother during pregnancy to assess the risk of common chromosomal aneuploidy abnormalities in the fetus. The target diseases are three common fetal chromosomal aneuploidy abnormalities, namely trisomy 21 (Down syndrome), trisomy 18, and trisomy 13.
The first high-throughput sequencing application approved by the drug regulatory authorities in China comes from BGI Gene, a subsidiary of BGI Group. The company has provided nearly 10 million non-invasive prenatal genetic tests. As far as I know, some regions in China (such as Hebei and Changsha) have also cooperated with BGI to carry out free non-invasive prenatal genetic testing projects in the local area.
If it is a pregnant woman over the age of 35, it is clinically recommended to do amniocentesis instead of peripheral blood, and the detection range will be wider and the results will be more accurate.
We once encountered a case where both husband and wife, who are Ph.D., categorically refused Down screening and other tests, saying that they had such a high education and IQ that they could not have a child like that. Even though we told them that it happened randomly, they still didn't believe it. Unfortunately, they ended up having a child with Down syndrome.
Macrosteptria is a B ultrasound examination, usually done around the 22nd to 24th week of pregnancy, mainly to check the development of the fetus in the womb. Because at this time, the fetus's head, face, heart and other parts have been basically formed, so its role is to eliminate most of the fetal malformations, such as congenital heart disease, cleft lip and palate.
But in any case, obstetric examination is the mechanism for finding birth defects, and there are many things we can do to avoid birth defects from the source. Good living habits and balanced nutritional intake can reduce the incidence of birth defects in a targeted manner.
For example, for the prevention of fetal neural tube defects, folic acid supplementation during pregnancy is very important. Maternal folate deficiency is one of the main causes of fetal neural tube malformations, and the intake of folic acid in the Chinese diet is significantly insufficient. Folic acid supplementation is clinically recommended from the first 3 months of pregnancy, as it is usually necessary to take folic acid orally for at least 3 consecutive months to bring the concentration of folic acid in the mother's blood to a level that is effective in preventing neural tube defects.
Finally, talk to "Mom and Dad-to-be", even if you really find out the problem, don't rush to give up. Now we have more accurate medical means, whether it is ultrasound imaging or genetic testing, which can help us more accurately determine the pathogenic genetic problems of the fetus in the womb and judge the future direction. Some birth defects are not as terrible as imagined, or there is a cure for them, and we can ensure the healthy growth and development of children after birth through intrauterine surgery and drug treatment, and even stem cell therapy.
(The author is Duan Tao, professor of Shanghai First Maternal and Infant Health Hospital affiliated to Tongji University)