September 12 is Birth Defects Prevention and Control Day. Birth defects are the nightmare of almost every prospective parent. However, what are birth defects? What are the causes? How can they be prevented during pregnancy? How can they be detected early? Mothers and fathers-to-be know very little. While the number of birth defects is increasing year by year, the level of scientific knowledge of preconception health care is not high.
According to national data, China is a country with a high incidence of birth defects and disabilities. Every year, about 200,000-300,000 children with visible congenital malformations are born, and the total number of children with congenital disabilities is 800,000-1.2 million, accounting for about 4-6% of the total number of births each year, and there is a trend of growth. The direct economic loss caused by neural tube abnormalities in China is more than 200 million yuan per year, the treatment cost of congenital stupidity is more than 2 billion yuan, and the treatment cost of congenital heart disease is up to 12 billion yuan. At the same time, the death and disability caused by birth defects also bring heavy psychological burden and immeasurable mental suffering to families. Such a status quo is not only a serious public health problem, but has become a social problem that affects economic development and people’s normal life. Therefore, to prevent birth defects, it is necessary to let families who are preparing for pregnancy as well as those who are pregnant know about birth defects, so that each family can be guided to achieve early prevention, early diagnosis and early intervention to reduce their incidence.
What are birth defects?
Birth defects, also known as congenital anomalies, are simply abnormalities in body structure and material metabolism caused by developmental disorders in the mother’s womb before birth. For example, the familiar congenital dysmorphism, harelip, cleft palate or the rare dwarf leprechaun syndrome, catcall syndrome, and the “seal fetus”, which is a fetus with a shortage of limbs due to a discontinued reaction during pregnancy, all fall under the category of birth defects.
What are the causes of birth defects?
Birth defects are caused by genetic and environmental factors as well as genetic-environmental interactions. Genetic factors include chromosomal abnormalities and genetic abnormalities. A common congenital dysmorphism is an abnormality in the number of chromosomes and an abnormality in the structure of chromosomes, such as cat-calling syndrome caused by the deletion of a segment of a chromosome, in which the child cries as if it were a cat. Genetic abnormalities are more common in China, such as thalassemia, which has a high incidence in the south, and is caused by mutations in a single pearl protein gene. Environmental factors include biological, chemical, physical and pharmaceutical factors, such as Toxoplasma gondii infection, which can cause multiple fetal malformations; plasticizers, which can affect the number of sperm in the offspring and shorten the reproductive organs of male fetuses; excessive radiation, which can cause chromosomal aberrations and breaks, resulting in fetal malformations; and aminoglycoside antibiotics such as streptomycin, which can cause deafness in newborns when applied during pregnancy. The most common neural tube abnormalities such as spina bifida and congenital heart defects such as ventricular septal defect are caused by genetic-environmental interactions.
Who is at high risk for birth defects?
Expectant mothers who have the factors mentioned below should put themselves in the high-risk group for birth defects and undergo relevant screening. Expectant mothers who have late childbearing over 35 years old or who have previously given birth to a child with birth defects are at increased risk for chromosomal abnormalities, etc. It is best to have an amniocentesis directly to understand the chromosomal situation; pregnant women with a family history of hereditary diseases or a history of consanguineous marriages are at risk for the occurrence of the corresponding family hereditary diseases and are at high risk for genetic abnormalities. Those who have been exposed to dogs and cats in early pregnancy or have rubella virus infection need to go for toxoplasmosis and virus testing during pregnancy; a history of indiscriminate medication in early pregnancy is also a high risk factor for birth defects; partial micronutrient deficiency in early pregnancy should be highly alert for neural tube malformation. Pregnant women with pre-pregnancy diabetes also have an increased incidence of malformations. Exposure to radiation or harmful substances such as lead and mercury in early pregnancy is associated with a high incidence of malformations, and early obstetric examination and diagnosis are also required. Other pregnant women with unexplained miscarriage, stillbirth, malformation or history of neonatal death or this pregnancy with excessive amniotic fluid, low amniotic fluid, fetal growth restriction, etc., are at high risk of birth defects.
How to prevent and treat birth defects?
There are three levels of prevention for birth defects in China, which can prevent the birth of most children with birth defects or reduce their symptoms.
The first level of prevention: to be carried out before pregnancy, including pre-marital medical examination and pre-conception health care, the common joke “check the ancestors”, in fact, there is some truth, to understand the unmarried parties in the past family has no hereditary diseases affecting the health of the next generation, the corresponding genetic expert consultation, to understand the risk of genetic diseases in the next generation, or even to The risk can be avoided. For example, hemophilia, which is inherited from the British royal family, is a sex chromosome inheritance, and if hemophilia is found before pregnancy, sex selection during pregnancy can prevent birth defects. Women should prohibit marriage between close relatives before pregnancy, choose the best age for childbirth, take folic acid supplements from 3 months before to 3 months after pregnancy, strictly control the safe use of drugs during pregnancy, and avoid exposure to toxic and harmful substances. Early detection and treatment of diabetes, etc.
Secondary prevention: After pregnancy, which means early pregnancy health care, reasonable nutrition, combined prenatal screening in early and middle pregnancy, including serological screening for chromosomal abnormalities such as congenital dysmorphism, ultrasound screening for large malformations, etc. For high-risk mothers, there are also amniocentesis and umbilical cord blood puncture for karyotype analysis or SKY testing. At present, the detection rate of chromosomal abnormalities in pregnant women with normal maternity checkups in Shanghai through combined screening is 95-97%, which is similar to that of developed countries. However, pregnant women who do not have regular maternity checkups often miss the diagnosis because they miss the time of joint screening, and the newborns with chromosomal abnormalities delivered at the Obstetrics and Gynecology Hospital of Fudan University in recent years were all pregnant women who did not undergo joint screening.
For some congenital heart disease, hydrocephalus and spina bifida caused by environmental factors or genetic-environmental factors interacting with each other, the diagnosis rate through ultrasound screening of large malformations is also high, but there are many factors affecting the prenatal diagnosis, such as whether the gestational week is appropriate, the thickness of the abdominal wall and the experience of ultrasound technicians. With the increasing advancement of prenatal diagnosis technology in recent years, more and more birth defects can be detected, but all of them require mothers-to-be to enhance their early pregnancy care and go to the maternity checkup to establish a card as early as possible, so that the fetus can be fully evaluated at the best gestational week and the most appropriate fetal position.
Tertiary prevention: refers to the screening of the baby after the fetus has been delivered, which is the collection of the baby’s heel blood. At present, we mainly carry out screening and diagnosis and treatment for congenital hypothyroidism, phenylketonuria, congenital hearing impairment, and also sericea in the south. Early diagnosis of defective children and selection of the best time for surgical correction can reduce the burden caused by defective children to families.
How can high-risk expectant mothers prevent birth defects?
The prevention of birth defects is very important. What expectant mothers can do on their own is primary prevention before pregnancy to achieve the best preparation and minimize harmful exposures before pregnancy. Mothers-to-be who are aware that they are at high risk for birth defects should take secondary prevention in a timely manner. As a guiding center for primary prevention of birth defects in Shanghai, the Obstetrics and Gynecology Hospital of Fudan University is responsible for providing a technical platform for promoting primary prevention of birth defects in all districts and counties of Shanghai, setting quality control standards, establishing preconception assessment systems and assessment indicators, developing appropriate technologies and conducting applied basic research, and has a complete set of diagnostic strategies for prenatal diagnosis of birth defects. So, what are the diagnosis and treatment strategies for secondary prevention?
4-9 weeks From early pregnancy, the mother-to-be is advised to start action by performing an initial ultrasound assessment: first, to accurately approve the gestational week, and then to rule out ectopic pregnancy; in the case of twins, this gestational week can also help verify whether the pregnancy is dizygotic or monozygotic. This is very important as many serious complications in the second trimester are associated with monozygotic twins.
10-14 weeks It is time for the mother to go to the hospital for her maternity check-up. At this time, there is a serum screening for early congenital dysmorphism and a nuchal translucency test for chromosomal abnormalities, which increases the risk of chromosomal abnormalities by 10 times.
16-20 weeks Serological screening for chromosomal abnormalities is performed in triplicate. Based on the results of the screening, the results of the early screening and nuchal translucency are combined and corrected to determine whether amniocentesis should be performed for karyotyping.
From 18 to 24 weeks, ultrasound screening is performed to detect all organs of the fetus, including the heart, brain, limbs and face. And many malformations such as cleft lip and palate, congenital heart disease, spina bifida, brain bulge, sacrococcygeal teratoma, etc. can be detected during ultrasound malformation screening.
In addition, in response to the current situation that congenital heart disease is the first birth defect in Shanghai, the Obstetrics and Gynecology Hospital of Fudan University has also pioneered the technique of fetal heart ultrasound screening for mothers-to-be with gestational diabetes mellitus or mothers-to-be with a previous family history of congenital heart disease.
28 Weeks – Full Term For mothers-to-be who have not undergone maternity checkups at the delivery hospital and have high-risk factors, high-risk ultrasound is specifically carried out so that a multidisciplinary joint consultation consisting of obstetricians, geneticists, pediatricians, ultrasound and MRI specialists can work together to provide relatively complete diagnosis and treatment recommendations for mothers-to-be on the basis of retesting of abnormal follow-up pregnancies.
Prevention of birth defects focuses on primary and secondary prevention, i.e., premarital, preconception and pregnancy interventions, all three of which are indispensable. By taking preventive measures in advance, parents can minimize the incidence of birth defects in their children, provide a guarantee for the upcoming life, and add a weight to the future “happiness index” of the family.