Year-end academic review of 2021: Advances in the field of birth defect prevention and control in China as of 2021

Prof. He-Feng Huang is an Academician of the Chinese Academy of Sciences; Fellow Honoris Causa of Royal College of Obstetricians and Gynecologists; Academician of the Third World Academy of Sciences; member of the Chinese Academy of Medical Sciences, and Director of the Institute of Reproduction and Development of Fudan University. Chair Professor, Doctoral supervisor, Chief physician at Fudan University, Shanghai Jiao Tong University and Zhejiang University, Visiting Professor at Hong Kong University and University of Adelaide, Australia. The chief scientist of the National 973 Program, the National “Twelfth Five-Year” Plan for Science & Technology Support Project, the National 863 Program, International Cooperation Project of China and Canada NSFC, The National Key Research and Development Program of China. Director of the Key Laboratory of Reproductive Genetics, Ministry of Education, China and Shanghai Key Laboratory of Embryo Original Diseases. Vice president of Chinese Maternal and Child Health Association, Vice president of Chinese Association for Improving Birth Outcome and Child Development; Founding Board Director of International Society of Reproductive Genetics. Editor for RBMO, JOVR, etc. By now she has published over 300 peer-reviewed papers, including Nature Medicine and PNAS. Birth defects, also known as congenital anomalies and malformations, may cause death of fetuses and infants, result in illness and long-term disability in children, and seriously affect the well-being of the population. Birth defects are a major public health concern in many countries worldwide, and we face severe challenges in preventing and controlling them. As the Chinese New Year approaches, we have invited Prof. He-Feng Huang to give us a review of advances in the field of birth defect prevention and control. Prof. Huang is an expert in reproductive medicine, an academician of the Chinese Academy of Sciences, and dean of the Reproductive and Developmental Research Institute of Fudan University. Human reproduction is a perennial issue, and fertility protection is a major challenge today Since the introduction of 2-child policy in 2015, China has only attained demographic dividend for a short period so far. It is estimated that the birth rate in China approached a record low in 2021 and the resulting shrinking and aging population has therefore become a pressing issue. As the Chinese society has progressed, the economic status of Chinese individuals has improved. The nature of their employment has changed accordingly, as has their attitude toward childbearing. Many countries across the world have evolved through different stages of development into their current state. Birth rates during this process are almost consistent with the economic development curve. China demonstrates the same trajectory. We should learn from international practices while considering our national conditions in order to improve births, such as reforming reproductive policies, systems, and supporting facilities. From a medical perspective, protecting fertility, preventing potential impairment, and improving fertility are major topics in obstetrics and gynecology, especially in the field of maternal and child health care. Maternal health care initiatives aim to prevent diseases in women so that they show normal fertility while remaining healthy. An increasing infertility rate is one of the main contributors to the decline in birth rate in China. Textbooks have noted that “under normal circumstances, 85% to 95% couples who have regular and unprotected sexual intercourse will conceive naturally within 1 year”. A small sample survey supported by World Health Organization followed up healthy couples preparing for pregnancy in China and found that the proportion of natural pregnancy within 1 year was around 70%. Assisted reproductive technology is an effective way to treat infertility, but spontaneous pregnancy is a mainstay to ensure that the population remains stable and should be supported. The 2012 Report on the Prevention and Treatment of Birth Defects indicates that the incidence of birth defects in China is approximately 5.6%, the number of new birth defects is approximately 900 thousand to 1 million every year, and the occurrence of birth defects is on the rise. Birth defects refer to abnormalities in the shape, structure, function, or intelligence of an infant before or at birth, which can seriously affect China's economic and social development. The causes of birth defects are complex, including environmental and genetic factors as well as interactions between them. Hereditary factors account for 30% of all birth defects, including chromosomal or genetic abnormalities. With advances in medical care, birth defects caused by nutrition and environmental factors have significantly reduced, but challenges persist in the prevention and control of birth defects caused by hereditary and unknown reasons. Genetic interventions through new technologies, such as pre-pregnancy screening and pre-implantation genetic testing, can reduce birth defects. This is the focus of current scientific research. In summary, natural conception is the most desirable outcome. For the health and well-being of human beings, we should try to eliminate hereditary birth defects occurring for both known and unknown reasons. China faces severe challenges in the prevention and control of birth defects The challenge is 2-fold. Firstly, the incidence of birth defects remains high. Although there are no official data, it is generally believed that the birth defect rate has not declined in recent years. Secondly, women of advanced maternal age are increasing and account for 15% or more of the total pregnant population. This group has higher risk of bearing babies with chromosomal aberrations than other age groups. Previous studies have shown that the probability of bearing babies with chromosomal abnormalities for women aged 40 years is 1 in 50, while for women over the age of 43, the probability is 1 in 20. Therefore, an increasing number of women becoming pregnant at an advanced age exerts tremendous pressure on the prevention and control of birth defects. In addition, the incidence of infertility is increasing annually, and babies born through assisted reproductive technology account for 2% to 3% of the total births. Babies born via this method are at an increased risk of suffering from chronic diseases in adulthood; that is, they are highly susceptible to metabolic diseases, cardiovascular diseases, tumors, and neuropsychiatric diseases. This kind of development original diseases impose a heavy burden on the national health expenditure. Another challenge raises from adverse environmental factors, such as outdated ideas surrounding childbirth, mental disorders, reduced physical exercise, unhealthy diet, and environmental pollution, exacerbate the issue. For example, 30 years ago, teratospermia was diagnosed when more than 20% of the sperm in a sample were deformed. In recent years, however, as the sperm quality of men has declined, sperm are considered normal as long as 4% have normal morphology. This means that such sperm are considered “normal,” even if 96% of them are in an abnormal state. Lowering the diagnostic criteria for sperm quality may pose an additional challenge to the prevention of birth defects. As the society progresses, people's attitudes change, and so do their actions, sometimes in destructive ways. The number of individuals with sexually transmitted diseases, drug addiction, AIDS, obesity, and other diseases in China is on the rise. These individuals may expose their offspring to the risk of birth defects. Our government should attend to this pressing situation, and medical institutes should dedicate themselves to developing new technologies to address the problem. In addition, some birth defects are not caused by heredity, but caused by de novo chromosomal or genetic abnormalities. Such mutations are difficult to prevent and sometimes cannot be identified until a child is diagnosed with related problems. New technologies might enable accurate diagnosis in utero to prevent major birth defects. Typical technologies, such as non-invasive cellfree DNA testing, can detect emergent fetal chromosomal abnormalities with circulating blood from pregnant women. Our team are working to develop new non-invasive prenatal testing (NIPT) technologies to identify baby's de novo gene mutations. New prenatal diagnosis technologies would throw a light on early intra-uterine intervention, diagnosis, and treatment of birth defects with complex causation and high disability and fatality rates. Advances in prenatal diagnosis technology Medical imaging With advances in medical imaging, from A-type ultrasound, B-type ultrasound to multi-dimensional stereo ultrasound, fetal growth and organ structure in the uterus can be observed, thus enabling the diagnosis of congenital heart disease, anencephaly, and other conditions. Fetal magnetic resonance imaging has been widely used for the screening and diagnosis of prenatal fetal malformations. China has a huge birth population, and screening via imaging is indispensable for diagnosing intra-uterine fetal diseases. In addition, intra-uterine fetal structural abnormalities found via imaging provide phenotypes for more accurate diagnosis of chromosomal or gene abnormalities. Genetics Technologies in the field of genetic diagnosis have developed rapidly in the past 2 decades, from observation of chromosome morphology under an ordinary microscope to full-exome and whole-gene sequencing. Early diagnosis of microdeletion and microduplication syndromes (MMSs) and monogenetic and oligogenic diseases is now possible. Children with mental retardation can be diagnosed by genetic and chromosomal screening. In the past, we conducted a comprehensive risk assessment of Down syndrome via biochemical methods, measuring the levels of specific markers in matern

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