Fetal Growth Restriction

　　The etiology of fetal growth restriction has not been fully elucidated to date. About 40% of the patients occur in normal pregnancy, 30% to 40% occur in pregnant women with various diseases and pregnancy complications, 10% due to multiple pregnancies, 10% due to fetal infection or malformation. The following factors are all related to the occurrence of this disease.

　　I. Fetal Factors

　　1. Genetic FactorsThe difference in birth weight of the fetus comes from 40% of the genetic factors of the parents, with the mother's inheritance and environmental factors being more significant.

　　2. Fetal InfectionThe fetal infection accounts for about 10% of the causes. Pathogens include viruses, bacteria, and protozoa.

　　II. Placental Factors

　　The placenta provides nutrition and oxygen to maintain the life of the fetus. Therefore, abnormalities in placental structure and function often lead to this disease.

　　III. Maternal Factors

　　The intrauterine growth and development of the fetus reflects the balance between the fetus, placenta, and mother. Any factor that damages the stability of the maternal internal environment, such as malnutrition, deficiency of trace elements, smoking and drinking, drugs, and others, can lead to fetal growth restriction.

　　Fetal growth restriction can be complicated by intrauterine hypoxia, intrauterine distress, perinatal death, and others. Due to the relatively small liver, glucose needs to be supplied to the relatively large brain, so neonatal hypoglycemia often occurs after birth. The physical development of the newborn is normal after birth, but due to hypoxia during the perinatal period, there are often neural injuries.

　　In the prevention of this disease, amniocentesis, amniotic fluid culture, karyotype analysis, or alpha-fetoprotein determination can be performed at 16 weeks of pregnancy to prevent the birth of malformed fetuses. Smoking during pregnancy can affect the growth and development of the fetus, and the harm of smoking to pregnant women should be publicized. Strengthen the prevention and treatment of pregnancy complications. Pregnant women should strengthen nutrition, not be biased in their diet, and should eat more protein and vitamin-rich foods to prevent any impact on the growth and development of the fetus.

　　The main examination methods for this disease are as follows:

　　1. Urine estriol determination

　　Urine estriol determination can assist in diagnosing placental function. In the endocrine匀称型, the urine estriol value curve is between the normal value and 2 standard deviations, showing a parallel state; in the exogenous不匀称型, unless there is adrenal developmental malformation, otherwise the urine estriol value will still match the normal value until 37 weeks of pregnancy, and then it will no longer increase, so that by 38 weeks of pregnancy, it will be below 2 standard deviations, indicating serious functional deficiency. If the urine estriol value decreases linearly, it often indicates that the fetus is in danger.

　　2. Determination of pregnancy-specific protein (SP1)

　　After 28 weeks of pregnancy, if the SP1 value is less than the 10th percentile, it often indicates fetal growth restriction.

　　3. Ultrasound examination

　　For those suspected of having fetal growth restriction, ultrasound measurement of the biparietal diameter of the fetal head should be performed every 2 weeks. The biparietal diameter of a normal fetus grows rapidly before 36 weeks of pregnancy. If the biparietal diameter of the fetal head increases by less than 2mm every 2 weeks, it indicates fetal growth restriction; if it increases by more than 4mm, it can exclude fetal growth restriction.

　　4. Umbilical artery velocity waveform

　　The application of umbilical artery velocity waveform can detect this disease early. By observing the fetal placental vascular dynamics through the peak S/D ratio of umbilical artery contraction (S) and relaxation (D) blood flow, it can be seen that the S/D ratio decreases gradually with the increase of gestational age, indicating good fetal development; the ratio increases indicates an increase in placental blood flow resistance, indicating poor fetal development.

　　Pregnant women should improve the quality of their diet and increase the intake of protein. It is best to ensure the intake of 2 eggs per day. Due to the different types and quantities of amino acids contained in various types of meat and milk from cows and sheep, pregnant women must accept various foods. A reasonable combination of meat and vegetables can improve the nutritional status. More fresh vegetables and fruits should be consumed. As long as it is detected and managed seriously in the middle of pregnancy, most growth-restricted fetuses can be corrected. If the diet adjustment still does not satisfy after that, compound amino acid injections can be administered intravenously.

　　In the treatment of this disease, there are mainly the following measures.

　　1. General Management

　　1. Bed rest: The pregnant woman should take a left lateral position, which can restore renal blood flow and renal function, thereby improving uteroplacental blood supply.

　　2. Umbilical cord blood puncture: Umbilical cord blood puncture can directly enter the fetal circulation, provide nutrition for the fetus, and improve the acid-base state of the fetus.

　　3. β2-adrenergic agonists: Salbutamol (Ventolin) and other drugs can dilate blood vessels, relax the smooth muscles of the uterine body and cervix, improve uteroplacental blood supply, and achieve good results in the treatment of fetal growth restriction caused by diseases such as preeclampsia, pregnancy complicated with chronic nephritis and chronic hypertension. Other vasodilators, such as aminophylline and magnesium sulfate, can also increase the uteroplacental blood supply by 21%-45%.

　　4. Low-dose aspirin and dipyridamole therapy: Aspirin and dipyridamole can reduce thromboxane synthesis, increase the ratio of prostacyclin (prostacyclin) to thromboxane, and thus achieve the purpose of improving uteroplacental blood circulation.

　　2. Obstetric Management

　　1. If there is no progress in the determination of fetal biparietal diameter, uterine fundal height, etc. after treatment for fetal growth restriction without internal medicine or obstetric complications and complications, pregnancy can continue.

　　2. If there are internal medicine or obstetric complications, even if it has not reached 37 weeks of gestation, termination of pregnancy should still be considered. Amniocentesis should be performed to understand the maturity of the fetus when terminating pregnancy.

　　3. For those who need to terminate pregnancy before 36 weeks of gestation, dexamethasone 5mg intramuscular injection, once every 8 hours, or 10mg intramuscular injection, twice a day, for a total of 2 days, can be used to promote the production of fetal pulmonary surfactant substances.

　　3. Neonatal Management

　　Due to fetal hypoxia in this disease, fetal meconium aspiration is likely to occur, so a skilled neonatologist should be present to handle newborns. Clean the respiratory tract below the vocal cords, remove meconium, and prepare for neonatal resuscitation and emergency care. Feed sugar water early to prevent hypoglycemia and pay attention to hypocalcemia. Prevent infection and correct complications such as polycythemia.