Macrosomia

　　Macrosomia is the result of the combined action of various factors, which is difficult to explain with a single factor. Clinical data show that only 40% of macrosomic fetuses have various high-risk factors, and the other 60% of macrosomic fetuses have no obvious high-risk factors. According to the description of Williams' obstetrics, common factors leading to macrosomia include diabetes, parental obesity, multiparity, prolonged pregnancy, maternal age, fetal sex, macrosomia of the previous fetus, race, and environment, etc.

　　1. Gestational diabetes

　　Whether it is gestational diabetes or diabetes mellitus during pregnancy, the incidence of macrosomia is significantly increased.

　　2. Obesity

　　Excessive weight and obesity in pregnant women have adverse effects on both the mother and the newborn.

　　3. Prolonged pregnancy

　　Prolonged pregnancy is significantly correlated with macrosomia, and the incidence of macrosomia in prolonged pregnancy is significantly higher than that in term pregnancy.

　　4. Polyhydramnios

　　Macrosomia often coexists with polyhydramnios, and the causal relationship between the two is not clear.

　　Difficult labor is a major complication of macrosomia. Due to the increased volume of the fetus, the head and shoulders are the main parts of difficult labor. The significantly increased rate of dystocia brings a series of complications to the mother and child.

　　1. Cephalopelvic disproportion

　　Since the fetal head of macrosomic fetus is larger, it causes the pelvis of pregnant women to be relatively narrow, and the incidence of cephalopelvic disproportion increases. In cases where the biparietal diameter of the fetal head is large, the fetal head does not enter the pelvis until labor. If the fetal head is placed above the inlet of the pelvis, it is called a positive sign of transverse lie, manifested as an extended first stage of labor. If the biparietal diameter is relatively smaller than the thoracoabdominal diameter, the descent of the fetal head is obstructed, and it is easy to cause an extended second stage of labor. Due to the prolonged labor, secondary uterine atony may occur; at the same time, the uterine volume of macrosomic fetus is large, and the tension of uterine muscle fibers is high. Over-stretching of muscle fibers is easy to cause primary uterine atony. Uterine atony in turn leads to abnormal fetal position, prolonged labor, postpartum uterine atony, laceration of soft birth canal, postpartum hemorrhage, and other complications. Due to the increased rate of dystocia, the incidence of cesarean section and vaginal surgery (forceps, vacuum extraction) increases. In underdeveloped areas, uterine rupture can occur if not treated in time. In urban areas, the cesarean section rate of macrosomic fetus can increase due to the prevention of dystocia.

　　2. Shoulder dystocia

　　For macrosomic fetus delivered vaginally, the incidence of shoulder dystocia increases, especially for macrosomic fetus with diabetes. Rouse et al. reported that the incidence of shoulder dystocia in neonates with birth weight >4500g from non-diabetic pregnancies is 15%. However, in pregnant women with gestational diabetes, the incidence of shoulder dystocia in the three groups is 1.2%, 14%, and 50% respectively.

　　If shoulder dystocia is not handled properly or delayed, serious complications can occur, even life-threatening, such as neonatal asphyxia, meconium aspiration syndrome, and various birth injuries. Head injuries can include scalp hematoma, intracranial hemorrhage, facial nerve palsy, brachial plexus injury, clavicle fracture, humerus fracture, and even diaphragmatic nerve injury.

　　3. Neonatal diseases

　　Since patients with gestational diabetes are prone to have macrosomic fetus, complications such as diabetes in the fetus or neonate can occur in macrosomic fetus.

　　The main symptom of macrosomic fetus is that the fetus is too large. Due to the large size of the fetus, pregnant women may experience symptoms such as abdominal pain and difficulty breathing. To date, there is no accurate method to estimate the weight of the fetus in utero. Most macrosomic infants are diagnosed after birth. The commonly used methods to predict fetal weight are clinical measurement and ultrasound measurement.

　　The occurrence of macrosomic fetus is greatly related to the behavior and habits of pregnant women during pregnancy. To prevent the occurrence of macrosomic fetus, it is recommended that pregnant women pay attention to the following two points:

　　1. Diabetes screening

　　Since macrosomia is closely related to gestational diabetes, it is necessary to screen for diabetes in all pregnant women between 24 and 28 weeks of pregnancy, and to treat gestational diabetes and abnormal glucose tolerance promptly and correctly.

　　2. Nutritional guidance for pregnant women

　　It is important to pay attention to perinatal health care for pregnant women and mothers. By providing nutritional counseling and guidance to pregnant women, and conducting prenatal health exercises and appropriate physical activities, the incidence of macrosomic fetus has shown a decreasing trend.

　　The measurement of large for gestational age infants can be calculated based on fundal height, abdominal circumference, and the height of the presenting part. Fetal weight ≥ 4000g may be a large for gestational age infant. It can also be predicted by B-ultrasound to measure the biparietal diameter, abdominal circumference, and femur length of the fetus to predict fetal weight. When the biparietal diameter of the fetus is >10cm, and the abdominal circumference/femur length >1.385, 80% to 85% are large for gestational age infants.

　　It is necessary to have a reasonable and balanced diet during pregnancy to prevent obesity. During the middle and late pregnancy, in addition to sufficient nutrition, pregnant women should try to control excessive intake of high-fat and high-calorie foods to prevent the fetus from being large. If the growth and development of the fetus is found to be too fast, it is advisable to consult a doctor to adjust the diet structure reasonably.

　　Experts specially remind that the nutritional status of pregnant women has a great impact on the development of fetal brain tissue. In the early pregnancy, when the embryo is still small, adding some foods rich in vitamin B, mainly including grains, sour porridge, vegetables, and fruits, can be beneficial; in the middle pregnancy, as the fetus grows rapidly, all organ systems are in the stage of differentiation and foundation, the heat consumption and protein needs of pregnant women increase by 10% to 20% compared to normal people, so the diet should mainly include dairy products, meats, eggs, beans, vegetables, and fruits; in the late pregnancy, the fetus is in the stage of skeletal development, subcutaneous fat accumulation, and weight gain, in addition to appropriate carbohydrates and protein foods, pregnant women can also increase fat-containing foods appropriately.

　　Large for gestational age fetuses need to prevent dystocia and asphyxia and actively treat various primary diseases and their complications.

　　1. Suspected large for gestational age fetus during pregnancy

　　At this time, a glucose screening test should be performed to detect diabetes early. Blood glucose should be controlled actively.

　　2. Normal pelvis and fetal position

　　Such pregnant women can try labor under close observation, and cesarean section should be performed if the labor progress is not smooth.

　　3. Vaginal delivery of large for gestational age infants

　　At this time, attention should be paid to shoulder dystocia, and timely measures should be taken if shoulder dystocia occurs.

　　4. Postpartum care of newborns

　　Large for gestational age infants may not be mature, especially for those with diabetes in the mother, who need to be cared for more intensively and monitored for complications. Close observation of vital signs changes, monitoring of blood glucose, jaundice, and other relevant biochemical tests, and transfer to a neonatal intensive care unit if necessary.