fetal growth restriction
Introduction
Introduction to fetal growth restriction Fetal growth restriction (FGR), also known as placental dysfunction syndrome or fetal malnutrition syndrome, refers to the fetal weight below the twentieth age of the average weight of the 10th percentile or less than the average weight of 2 Standard deviation. Fetal growth and development are closely related to many factors, such as the external environment of pregnant women, the pathophysiological conditions of pregnant women, the placenta and umbilical cord, the internal environment of the fetus itself, and the sperm status before pregnancy. These factors, such as a decrease in the number of fetal cells, or abnormal cell size, can lead to small or large children. basic knowledge The proportion of illness: 0.0003% Susceptible population: pregnant women Mode of infection: non-infectious Complications: meconium aspiration syndrome neonatal asphyxia
Cause
Fetal growth restriction etiology
(1) Causes of the disease
The etiology of fetal growth restriction has not yet been fully elucidated, about 40% occurred in normal pregnancy, 30% to 40% occurred in pregnant mothers with various diseases and pregnancy complications, 10% due to multiple births, 10% due to fetal problems - Infection or malformation, the following factors may be related to the occurrence of FGR.
Fetal factors (35%):
(1) genetic factors: the difference in fetal birth weight, 40% from the genetic factors of the parents, with the mother's genetic and environmental impact, genetic factors are the key to determine the incidence of FGR, so FGR is associated with various genetic diseases, Atlanta, the United States In the report of the congenital defect project, the FGR of the chromosomal abnormalities was more than 38%, and the risk of major malformation in the FGR was about 8%. Although the number is small, the burden caused by these malformations is very high. Obviously, prenatal diagnosis is the focus of obstetricians dealing with FGR.
Clinically, the autosomal trisomy is the most common karyotype abnormality. In the above-mentioned Atlanta report, these account for 88% of all chromosomal abnormalities, and the 21-trisomy is the most common of these abnormalities, and its incidence is about 1:660 births, 1/3 of newborns are FGR, the relative risk of FGR in 21-trisomy is increased by 4 times, the incidence of 18-trisomy is about 1:3000, and newborns are 1 year. The survival rate is 10%, the relative risk of FGR is 46.3, and the incidence of 13-trisomy is 1:5000. It has the same prognosis as the 18-trisomy. More than half of the newborns are FGR. The relative risk of FGR is increased by 9 times. FGR is associated with other karyotypic abnormalities, including 45, Turner's syndrome, and cri-du-chat syndrome.
(2) Fetal infection: fetal infection accounts for about 10% of the cause of FGR. Pathogens include viruses, bacteria and protozoa.
Placental factor (25%):
The placenta provides nutrients and oxygen to maintain the life of the fetus, so abnormalities in the structure and function of the placenta are the cause of FGR.
Multiple births are one of the factors in the occurrence of FGR, and the incidence of multiple fetuses is 10 times higher than that of singles.
Maternal factor (20%):
Intrauterine growth and development reflects the balance between the fetus, the placenta and the mother. The fetus relies on the mother's adequate nutrient supply and the ability of the mother to transport sufficient nutrients through the vascular branches into the fetal placenta unit. Any damage to the mother's environment is stable. Can lead to adverse growth and development of the fetus.
(1) Nutritional factors: maternal nutritional status affects fetal growth and development. This effect is related to the maternal potential nutritional status and the period and nature of malnutrition. Through observation and intervention studies, it is found that maternal malnutrition is moderate to fetal birth weight. Influence, in the Dutch famine from 1944 to 1945, if the calorie restriction was lower than 6280kJ (1500kcal) per day, the average birth weight decreased by 300g. In clinical practice, the function of the parent gastrointestinal tract plays an important role in the occurrence of FGR. .
The relationship between maternal nutrition and birth weight is very close. Pregnant women's nutrition is the basic source of fetal nutrition. Therefore, malnutrition in pregnant women, lack of protein and heat card, not only affect fetal growth and development, but also affect the mental development of the baby after birth. Some people in the two groups of pregnant women were given a difference of 2511.3kJ (600kcal) per day. The group with high calorie and high protein had a birth weight of 250g compared with the other group. In 1929, the Philippines reported that the pregnant women were rich in nutrition. Ordinary or worse, the incidence of low body weight was 3.2%, 11.0% and 31.0% respectively. In 1979, the Shanghai Institute of Pediatrics reported that 1/4 (9/35 cases) of the small sample was due to partial eclipse of pregnant mother and severe morning sickness. Eating less or lacking dishes due to living in remote mountainous areas, Tatari et al reported in 1980 that a large number of manual labor during pregnancy and undernourished people are less likely to produce small samples than those with light physical labor.
(2) Trace elements: In recent years, studies on trace elements have found that half of the pregnant mice with severe zinc deficiency during pregnancy have abortion. The surviving mice have a birth weight of only half of normal, and 90% have various malformations. If the whole process of pregnancy gives mild low-zinc food, the surviving pups show stunting and the survival rate is reduced. According to the data of the Obstetrics and Gynecology Hospital of Shanghai Medical University, the blood zinc of FGR children is found through the study of trace elements in normal children and FGR children. The contents of iron, selenium, vanadium and manganese are lower than those of normal children. Therefore, it is believed that FGR may be related to the deficiency and imbalance of various trace elements. Therefore, it is considered that the determination of trace elements during pregnancy has guiding significance for pregnancy care. The need for internal growth and development should be reasonable to take nutrients, not partial eclipse, should be foods rich in zinc, iron, copper, manganese, selenium, such as fish, eggs, lean meat, animal liver, kidney, soy products, kelp, fresh vegetables and Fruit and so on.
(3) uterine placental perfusion: uterine placental blood perfusion caused by FGR accounted for 1/3, pregnancy-induced hypertension syndrome, chronic nephritis, high blood pressure pregnant women due to poor uterine placental perfusion easily lead to FGR, hypertension in pregnant women in the arteries Angiography and uterine vascular stenosis can be seen during angiography. In pregnant women with pregnancy-induced hypertension, placental implant sites, common obstructive arterial vascular necrosis, according to the 1982 Shanghai Medical University Obstetrics and Gynecology Hospital, in 232 cases of intrauterine growth Among the restrictions, 26.1% were caused by pregnancy-induced hypertension, 6.4% were chronic hypertension, 18.5% were twins, 12.7% were other diseases, 1.3% of fetal congenital malformations, and 37.5% were not found.
(4) Effects of tobacco, alcohol and certain drugs: smoking in pregnant women, because carbon monoxide and nicotine can reduce placental perfusion and blood carrying O2, and through the placenta into the fetus, the incidence of FGR is related to the amount of smoking, smoking more than 1 box per day The incidence of FGR is 12%, which is 3 times higher than that of non-smokers. Ethanol can affect pancreatic function directly or by its metabolite glyoxylic acid, hindering the absorption of fat and fat-soluble vitamins (A, B, E, K). Therefore, chronic alcoholism can induce a uniform FGR. The use of antihypertensive drugs reduces the dynamic pressure, and also reduces the blood flow of the uterus and placenta, affecting the intrauterine growth and development.
Other (10%):
In recent years, with the research and development of molecular biology, the influence of maternal and child endocrine factors on FGR has been widely concerned by scholars. The lack or loss of certain growth factors or enzymes may be the risk factors for FGR. It has been suggested that FGR is related to the growth medium of the fetus itself, such as epidermal growth factor and insulin-like growth factor deficiency. It is known that zinc can promote the secretion of insulin and fetal growth hormone, and whether the lack of its factor is directly related to zinc deficiency, further research is needed. .
There are three types of factors that can affect the intrauterine growth and development of the fetus.
(two) pathogenesis
1. FGF's malformation caused by genetic factors includes central nervous system, cardiovascular system, gastrointestinal tract, genitourinary system, musculoskeletal system and craniofacial malformation. Although it has confirmed congenital malformation accompanied by FGR, its The pathogenesis of concomitant disease is still unclear. Is FGR causing congenital malformation? Or the presence of congenital malformation tends to FGR? In karyotypic abnormalities, it is apparent that there is an intrinsic chromosomal disease, and finally FGR is caused. In theory, an unknown mechanism must be considered to cause both congenital malformations and FGR. Answering this question can solve normal or abnormal fetal growth and development.
2. The pathogenesis of FGR caused by fetal infection is still unclear. Through the study of perinatal infection results of cytomegalovirus and rubella, it is found that several mechanisms can eventually lead to FGR, through the placenta, after fetal infection with cytomegalovirus, pathological manifestations Mainly cell lysis, in the subsequent healing process, edema, inflammation, fibrosis, occasional calcification, this process not only loses important cellular components, but also replaces non-functional cells, which leads to anatomical changes, which in turn reduces Function, on the contrary, the fetus is infected with rubella, which can cause vascular insufficiency caused by small vessel endothelial damage, delaying cell division, which is not conducive to organ formation. After the cell is infected with rubella virus, cell lysis is not the pathogenesis of congenital rubella syndrome. Mainly, various pathogenesis may affect these two perinatal infections, as well as the occurrence of FGR caused by other infections.
3. Abnormal placenta is seen in the absence of placental surface area that provides major nutrient exchange, and causes FGR. In the fetal sheep study with microsphere embolization of placenta circulation, birth weight was reduced by 30%, but in another study, FGR placental tissue There were no obvious pathological changes in the examination; some studies suggested that there were placental microvascular lesions, and there was occlusion in the third grade villus muscle layer. This may be the basis of FGR. In short, the characteristic placenta related to FGR Abnormalities have not been explained, and placental pathology is seen in a small fraction of FGR, and even in these cases, the causal relationship is still unclear.
4. The pathogenesis of FGR in multiple twins is poorly understood, but its growth and development will catch up in the neonatal period, indicating that the intrauterine environment of multiple pregnancies limits its growth and development, which may be due to excessive placental tissue limiting placental tissue. Growth leads to fetal growth restriction; it may also be caused by multiple maternal sharing of maternal nutrition.
The pathological manifestation of fetal growth restriction is: except for the characteristics of the birth weight below the 10th percentile, about half of the full-term FGR children have signs of subcutaneous fat deficiency, showing a boat-like abdomen, pale skin, and drying quickly. , split, often in the palm of the hand, the soles of the feet, the front abdominal wall and the extremities of the limbs, the umbilical cord is often fine and yellow stained, and the attitude is relatively experienced compared with normal weight children.
5. The nervous system In the early pregnancy, the development of the nervous system is mainly manifested by the increase of the number of neurons, and the late pregnancy is mainly the enlargement of cells, the branch of axons, and the formation of myelin, so the brain development is most susceptible. In the first half of pregnancy, the cerebellum is the fastest in the development of the brain, so it is most susceptible to intrauterine growth disorders. If the factors affecting the formation of FGR begin in early pregnancy, FGR can be awkward and intelligent. And so on.
6. Respiratory system from the 30th week of pregnancy, alveolar surfactant can be measured in amniotic fluid, the increase of surfactant in the fetal lung, mainly related to gestational age, and weight-related, so full-term FGR children and the same weight of premature birth Compared with children, the incidence of respiratory distress syndrome (RDS) is significantly reduced.
7. Adrenal cortex The adrenal cortex is different from that of adults. By birth, fetal belts account for 80%, and adult belts account for 20%. After birth, regardless of gestational age, fetal belts begin to degenerate rapidly, and adult belts increase within 1 to 5 weeks. Up to 50%, the stress function of newborns is mainly related to the function of adult belts. Because of the incomplete function of the placenta and the hypofunction of the adrenal cortex, the stress response is not as good as normal term infants and less than the premature infants of the same weight.
8. Body temperature regulation of premature FGR children due to immature sweat gland development, so sweating function is limited, full-term FGR children have sweating function, and in the cold, the heat production reaction is also better, but because of the low energy storage, easy to exhaust It can not protect against cold, and it is easy to cause severe hypoglycemia, so it should be kept warm.
9. Metabolic characteristics In addition to the low glycogen storage of FGR, the gluconeogenesis is also poor. This is the comprehensive cause of hypoglycemia in FGR children. The fasting blood glucose value of FGR in the first 3 hours of birth is 2.2-2.6mmol/ L (39 ~ 47mg / dl), if not timely feeding or intravenous glucose, can be reduced to 1.6 ~ 0.6mmol / L (30 ~ 10mg / dl) within 2 ~ 36h, resulting in symptomatic or asymptomatic hypoglycemia, If left untreated, it can cause death or cause sequelae of the nervous system. Premature FGR is complicated by hypoxia or hypothermia, and the incidence of hypoglycemia is the highest. The tolerance of intravenous glucose supplementation in FGR is better than that of premature infants with the same weight. The normal term infants with gestational age are poor, and the lower the birth weight, the worse the sugar tolerance of FGR children. If FGR children are not associated with symptoms, their sugar tolerance will be obvious in about 1 week with the increase of birthday age. improve.
The storage of fatty acids in FGR is relatively more than that of carbohydrates. The fatty acids, glycerol and ketone bodies in plasma rapidly rise to the highest value after birth. In addition, FGR often has intrauterine hypoxia, so most of them have different degrees of acidosis. It can be manifested as pale, weak and weak, poor circulation, decreased muscle tone, and increased difficulty in breathing. It is necessary to take timely measures.
The umbilical cord blood amino acids in full-term FGR children are similar to those in normal term infants, but after birth, FGR children show different levels, maintaining a constant alanine and proline concentrations from the beginning. This amino acid difference is similar to that of malnourished babies. This is due to the decomposition of proteins to provide energy. The concentrations of ammonia, nitrogen, urea, uric acid, etc. are higher than normal in life and last for a long time.
10. Other
In the umbilical cord blood of FGR, there is a greater amount of erythropoietin than normal children, so there is a higher hematocrit after birth. Haworth reported that the average capillary hematocrit of severe FGR children immediately after birth was 73% ( There is a 10% difference compared with gestational age children, and the percentage of fetal hemoglobin is also high. Both blood and high fetal hemoglobin decrease gradually after 1 week of birth. Nodd envisions FGR convulsion and nervous system symptoms. Because of the high blood viscosity, it is an important reason for the increase in the incidence of massive bleeding in the lungs of FGR.
Prevention
Fetal growth restriction prevention
1. The internal cause of FGR is often caused by chromosomal lesions or fetal virus infection. Diagnosis should be made early. Amniocentesis, amniocentesis, karyotype analysis, or alpha-fetoprotein determination can be performed at 16 weeks of gestation to prevent malformation. The birth of the fetus, smoking during pregnancy can affect the growth and development of the fetus, and it is necessary to strengthen publicity.
2. The exogenous heterogeneous type FGR is caused by pregnancy-induced hypertension, multiple pregnancy, chronic nephritis or other medical diseases combined with pregnancy. The prevention and treatment of complications during pregnancy should be strengthened or stabilized, and the blood supply to the placenta will not be affected. Limited internal growth.
Pregnant women should strengthen nutrition, not partial eclipse, should eat more foods rich in protein and vitamins to prevent fetal growth and development.
Complication
Fetal growth restriction complications Complications meconium aspiration syndrome neonatal asphyxia
Fetal growth in children with fetal growth is prone to meconium aspiration syndrome, so that neonatal asphyxia is aggravated, and neonatal resuscitation should be done.
Symptom
Fetal growth restriction symptoms common symptoms fetal growth retardation pregnancy-induced hypertension placenta aging fetal intrauterine growth retardation hip production
1. Intrinsic allotype FGR At the beginning of pregnancy or in the embryonic stage, the determinants of the hazard have already occurred. It is characterized by the weight, head diameter and height of the newborn, but not proportional to the pregnancy; the number of cells in each organ is reduced. The brain is low in weight; half of the newborns are malformed and can endanger survival; the main cause is congenital or chromosomal lesions, viral or toxoplasmosis infections.
2. The external factors of FGR hazard factors only play a role in the third trimester of pregnancy. The internal organs of the fetus are basically normal, only nutrient deficiency, so the weight loss and head circumference and body length are not affected, which is characterized by uneven development of newborns. Head circumference and body are consistent with pregnancy and low body weight; appearance is malnourished or overripe; basic disease is due to placental dysfunction or disorder, often accompanied by pregnancy-induced hypertension, chronic nephritis, expired pregnancy and other causes.
3. The external factor FGR is a mixed type. Due to malnutrition, lack of important nutrients such as folic acid, amino acids, etc., the pathogenic factors are external factors, but they affect the whole pregnancy, so the consequences are similar to the intrinsic FGR. It is characterized by neonatal weight, body length and head diameter are reduced, and there is malnutrition status; the volume of each organ is small, the liver and spleen are more serious, the number of cells can be reduced by 15% to 20%, and some cells are also reduced in size.
The clinical status of FGR is divided into 3 types, and the prognosis of neonates with internal factors is the most unsatisfactory.
Examine
Fetal growth restriction test
Urinary estriol assay
Can assist in the diagnosis of fetal, placental function, in the internal factor FGR, the urinary estriol value curve is between the normal value and 2 standard deviations, in a parallel state, in the exogenous unequal scale FGR, unless there is Adrenal gland developmental malformation, until the 37th week of gestation, the urinary estriol value is consistent with the normal value, and then no longer grows, so that by 38 weeks of pregnancy, under 2 standard deviations, indicating severe functional deficiencies, if urine The estriol value plummets, often indicating that the fetus is at risk.
Determination of pregnancy specific protein (SP1)
After 28 weeks of gestation, if the SP1 value is less than the 10th percentile, it is more likely to have fetal growth restriction, so the SP1 value has certain value and can be used for clinical reference.
Ultrasonography
For those suspected of fetal growth restriction, the fetal head double top diameter should be systematically ultrasonically measured every 2 weeks to observe the growth of the fetal head double top diameter. The normal fetus grows faster before the 36th week of pregnancy. If the growth of the fetal head double top diameter is <2mm every 2 weeks, the growth of the fetus is limited. If the growth is >4mm, the fetal growth restriction can be excluded.
In addition, B-mode ultrasound measurement of fetal thoracic anteroposterior diameter, abdominal transverse diameter and abdominal circumference can also predict the weight of low birth weight infants, which is more accurate in the thoracic circumference. In recent years, the application of foreign total uterine cavity volume (TIUV) can also be early Diagnosis of fetal growth restriction, the formula is V = 0.523 × ABC (0.523 is a constant), A = distance from the fundus to the internal cervix, B = transverse diameter of the uterine cavity, C = maximum anteroposterior diameter of the uterine cavity.
Umbilical artery velocity waveform
The umbilical artery velocity waveform can be used to detect FGR early. The systolic (S) and diastolic (D) blood flow peak S/D ratios of the umbilical artery can be used to observe the fetal vascular kinetics. The S/D ratio gradually increases with the gestational age. Decline indicates that the fetus is well-developed. If the ratio rises, the placental blood flow resistance increases, indicating fetal dysplasia to predict FGR.
Diagnosis
Diagnosis and identification of fetal growth restriction
diagnosis
Prenatal examination
In detail, carefully ask about the history of pregnancy, and those who have the possibility of FGR should be alert to the occurrence of FGR.
(1) Measurement of height and weight of the fundus: According to the height of the fundus, abdominal circumference, and weight of the pregnant woman, the size and growth rate of the fetus are estimated (due to the abdominal circumference, the weight of the pregnant woman is affected by many factors, so no diagnostic indicators are used, only for reference. ).
Under the premise of affirming the last menstrual period and gestational age, the height of the uterus is measured. After 28 weeks of gestation, if there are 2 consecutive prenatal clinic examinations, and the height of the fundus is less than the normal 10th percentile, there is the possibility of FGR. .
(2) In addition, attention should be paid to the weight of pregnant women. From the 13th week of pregnancy, the body weight increases by an average of 350g per week until full term. During the 13th to 28th week of pregnancy, the body weight of the pregnant woman due to pregnancy increases with its own body weight. Mainly, after 28 weeks of gestation, if the weight of the pregnant woman has not increased for 3 consecutive weeks, it is necessary to pay attention to fetal growth restriction, and pay attention to the presence or absence of pregnancy-induced hypertension or smoking.
The diagnosis of FGR is mainly to dynamically observe changes in the fundus height growth curve in the pregnancy map. The B-ultrasound can be used to monitor fetal development indicators. In addition, the fetal heart rate electronic monitor monitors the fetal heart rate curve and uses Doppler blood flow as much as possible. The figure is typed.
2. Postnatal diagnosis
(1) Birth weight: After birth, FGR will measure the birth weight, refer to the gestational week of birth, if it is lower than the 10th percentile of the weight of the gestational age, the diagnosis can be made. Department of Obstetrics and Gynecology, Shanghai Medical University A total of 20,844 cases of neonatal birth weight were delivered by the hospital through different gestational weeks. The gestational age weight scale and the 10th, 25th, 50th, 75th and 90th percentile values were used as reference for the diagnosis of FGR.
(2) Estimation of gestational age: It is very important to judge the gestational age of newborns with birth weight <2500g, because about 15% of pregnant women do not have correct menstrual history, plus vaginal bleeding in early pregnancy and menstruation confusion, modern contraception The widespread use of medicine, the history of menstruation is difficult to master, which brings difficulties for the estimation of gestational age. In practical terms, external observation is more important for the estimation of gestational age, and the posture is sophisticated, the ear shell can be touched and cartilage, and it is easy to form; The mammary gland is easy to touch the nodules; the foot is more textured; the nails are more than the fingertips; the testicles are falling, the scrotum is more creased; the labia majora can cover the labia minora; the muscle tension is better; the skin thickness is increased, accompanied by suede, and the skin color is lighter; The reflection is well completed, with adduction; holding the reflex can bring the baby's body up, etc., all suggesting that the gestational age is large, and the maturity of the bone can also provide a reference for estimating the gestational age.
Differential diagnosis
Mainly the identification of FGR children and premature infants, generally can be distinguished according to gestational age and body weight. For low-weight children whose gestational age is unknown, they can be identified from the aspects of appearance, skin, ear shell, breast, striate and external genitalia. FGR is still a premature infant. It is often found in the clinic that some low-weight children have edema without limbs, but the body is short of hair, but the ear shell is soft and not formed. The contradiction between the development of the breast nodules and the labia majora suggests that the premature FGR Possible.
