Cephalic dystocia

　　The formation of cephalic dystocia is complex and multifaceted, not caused by a single factor. The main factors affecting delivery include uterine contraction, birth canal, fetus, and psychological factors. These factors need to coordinate and adapt to each other during the delivery process for the fetus to be delivered smoothly.

　　1. Uterine power factors

　　During the delivery period, the fetus gradually descends through the birth canal due to uterine contractions, and the intensity and frequency of uterine contractions can provide information for predicting dystocia. Abnormal uterine power can be primary or secondary, caused by abnormal birth canal and fetal factors, making it difficult for the fetus to pass through the birth canal and leading to secondary uterine weakness. Abnormal uterine power includes: uterine contraction weakness (coordinated, hypotonic, and uncoordinated, hypertonic) and uterine contraction strength (coordinated, acute labor, and uncoordinated, tetanic or spasmodic contractions).

　　2. Birth canal factors

　　Abnormalities of the bony birth canal include pelvic contraction (flat pelvis, rachitic pelvis, anthropoid pelvis, funnel-shaped pelvis, small pelvis), malformed pelvis, and excessive pelvic obliquity. Abnormalities of the soft birth canal include vaginal septum and longitudinal septum, vaginal tumors, vaginal scars, cervical fibroids, rigid cervix, ovarian tumors or fibroids located in the pelvic cavity, etc.

　　3. Fetal factors

　　Abnormal fetal development includes macrosomia, fetal malformation (hydrocephalus, anencephaly, meningomyelocele, conjoined twins), etc. Abnormal fetal head position is often accompanied by malpresentation of the head and pelvis, which hinders the rotation of the fetal head to the anterior position. The most common is persistent occipitotransverse position and persistent occipitoposterior position, other than that there are also high-lying fetal head position, anterior malposition in the occipitotransverse position, face position, and frontal position.

　　4. Psychological factors

　　Delivery is a huge stress event for women, and anxiety and depression are the most common psychological responses. Appropriate anxiety accompanied by moderate activation of the sympathetic nervous system can improve an individual's ability to adapt to the environment; however, excessive anxiety is not conducive to environmental adaptation and can lead to a series of neuroendocrine changes within the body, such as decreased norepinephrine secretion, which weakens uterine contractions and increases sensitivity to pain. The intense pain of strong uterine contractions further increases the anxiety and tension of the mother, forming a vicious cycle that increases the rate of midwifery assistance and postpartum hemorrhage.

　　In addition to general symptoms, cephalic dystocia can also cause other diseases. The main complications of this disease include postpartum hemorrhage, hemorrhagic shock, and encephalopathy syndrome. Therefore, once detected, active treatment is needed, and preventive measures should also be taken in daily life.

　　Dystocia caused by malpresentation of the fetal head is known as cephalic dystocia. Cephalic dystocia is common in abnormal deliveries and is also one of the most difficult to diagnose. It accounts for 23.98% of the total number of deliveries and 81.63% of the total number of dystocias. In addition to obvious pelvic contraction, cephalic dystocia is difficult to diagnose before delivery, and the vast majority of cephalic dystocias only gradually manifest after a certain period of labor. Early identification of the signs of cephalic dystocia and proper treatment can improve the outcome of delivery. The clinical manifestations of cephalic dystocia mainly include the following aspects:

　　1. Premature rupture of membranes

　　It may be a sign of dystocia, due to malpresentation or abnormal position of the fetal head, which does not adapt to the pelvic inlet plane, resulting in a large gap between the fetal head and the pelvic inlet. This allows amniotic fluid to enter the amniotic sac in front of the fetal head. When uterine contractions occur, the amniotic membrane cannot withstand the pressure and rupture.Statistics show that nearly half of difficult labor cases experience premature rupture of membranes..

　　2. Abnormal labor curve

　　The initial clinical manifestation of difficult labor during the formation process is prolonged labor. Prolonged latent phase is often the consequence of primary uterine contraction weakness or suggests the presence of malposition of the pelvis or abnormal fetal head position. Prolonged or停滞 active phase, with dilation at 4-5 cm, often indicates that the fetal head is obstructed at the inlet of the pelvis, suggesting malposition of the pelvis or severe abnormal fetal position.

　　3. Prolonged or停滞 second stage of labor

　　Abnormalities in the second stage of labor can be caused by abnormal fetal head position, maternal exhaustion, secondary uterine contraction weakness, or because the mother cannot hold her breath downward. The second stage of labor is divided into the descent phase and the pelvic floor phase. Abnormalities in the descent phase require consideration of possible malposition of the pelvis. Generally, if the fetal head reaches the pelvic floor, it can be delivered vaginally. In the pelvic floor phase, the extended resistance often comes from the perineum and pelvic floor tissues. Delayed or停滞 descent of the fetal head may occur at the end of the first stage or during the second stage of labor, which is a late clinical manifestation of difficult labor.

　　4. Uterine contraction weakness

　　Primary and secondary uterine contraction weakness may occur. Primary uterine contraction weakness may be due to psychological and spiritual factors, severe malposition of the pelvis, or abnormal fetal head position. In cases where the pelvis is malpositioned or the fetal head is obstructed at the inlet of the pelvis, it may be difficult to distinguish from false labor. Due to malposition of the pelvis and abnormal fetal head position, resistance increases during the progress of labor, often manifesting as secondary uterine contraction weakness, with the fetal head obstructed at the middle pelvis or outlet plane..

　　5. Unengagement or delayed engagement of the fetal head

　　During labor, if the fetal head is floating and the cervix has not engaged or has not engaged by 5 cm of dilation, it indicates an abnormal engagement, suggesting severe malposition of the pelvis or abnormal fetal head position.

　　6. Abnormal fetal head position

　　Abnormal fetal head position is the primary cause of difficult labor. This includes abnormal presentation such as straight vertex position, obstruction of internal rotation such as persistent occiput posterior position and transverse position, abnormal fetal head posture such as fetal head extension presenting as anterior vertex, frontal, or facial presentations, and lateral flexion presenting as anterior malposition. Abnormal fetal head position may cause descent obstruction due to increased diameter of the fetal head during descent, delayed or停滞 cervical dilation, and secondary uterine contraction weakness.

　　7. Early straining, cervical-vaginal edema, and difficulty in urination

　　During the first stage of labor, due to the early compression of the rectum by the occiput, the patient may involuntarily hold her breath. In cases of malposition, the fetal head compresses the cervix for a long time, leading to diffuse edema. In anterior malposition, the anterior parietal bone enters the pelvis first, compressing the anterior vaginal wall and urethra, resulting in edema of the anterior vaginal wall, the anterior lip of the cervix, and difficulty in urination.

　　8. Maternal manifestations

　　Extended labor can lead to maternal exhaustion, often accompanied by restlessness and anxiety, sometimes with severe dehydration, manifested as dry mouth, cracked lips, loss of skin elasticity, and even elevated body temperature. In severe cases, there may be electrolyte imbalance and acid-base disorder. Physical examination may reveal intestinal distension, urinary retention, and even hematuria. Pathological uterine contractions, elongation of the lower uterine segment, elevation of the fundus, and even uterine rupture may occur. These symptoms are more pronounced when labor exceeds 20 hours, and delivery should be terminated as soon as possible.

　　9. Fetal manifestations

　　Fetal distress, severe fetal head edema (birth tumor) or hematoma, obvious craniocerebral overlap or deformation.

　　Abnormal fetal head position is the main factor causing difficult labor in the cephalic position. However, this general cephalopelvic disproportion caused by the poor flexion of the fetal head and the increase in the diameter of the fetal head passing through the pelvis has variability. Once the fetal head turns to the anterior position, the diameter passing through the pelvis decreases, and the cephalopelvic disproportion no longer exists. Correcting the fetal head position is the most important measure to prevent difficult labor in the cephalic position:

　　1. The fetal head position can be corrected during pregnancy or in the early stage of delivery by using body posture or techniques, or by manually turning the fetal head through the vagina after the cervix is dilated to 7-8cm during labor, which can reduce the incidence of difficult labor in the cephalic position. It is also necessary to provide reasonable nutritional guidance to pregnant women, avoid excessive nutrition and appropriate exercise, and reduce the incidence of macrosomia.

　　2. Regular prenatal examinations: Once pregnancy is confirmed, prenatal examinations should be carried out within three months, and then according to the doctor's instructions to go to the hospital for regular checks. During prenatal examinations, medical staff not only check the fetal position but also pay attention to whether the birth canal is abnormal, such as finding pelvic narrowing, it should be determined in advance what mode of delivery should be chosen (vaginal delivery or cesarean section). When the fetal position is abnormal, medical staff should also help adjust the fetal position according to the specific situation.

　　3. After admission to the hospital for childbirth, the mother should pay attention to appropriate rest and diet, and not be overly anxious and fearful psychologically; medical staff should carefully observe the progress of labor, make correct judgments, and handle them in a timely manner. In addition, the correct handling of difficult labor depends on the experience of medical staff, and it is absolutely forbidden to use催生针 during the labor process, especially muscle injections of oxytocin and other催生针, which should be strictly prohibited before delivery.

　　Difficult labor in the cephalic position refers to the difficulty in childbirth caused by the position of the fetal head or the poor flexion of the fetal head. The normal position of the fetal head should be the occiput facing the mother's left or right front, with the fetal head flexed and the occiput position lowest. The main examinations for difficult labor in the cephalic position include physical examination and ultrasound examination.

　　1. The fetal back is not easily palpable in the abdomen, and it may be possible to feel the fetus's body and the fetal heartbeat is often on one side of the maternal abdomen or near the midline of the abdomen.

　　2. Digital examination often feels a larger space in the posterior half of the pelvic cavity, and the pubic symphysis is tightly engaged with the fetal head. If it is a posterior position, it is easy to feel the large foramen magnum located in the left or right front of the pelvis; if it is a transverse position, it is easy to appear thickening of the anterior lip of the cervix, which is actually edema.

　　3. Vaginal examination shows that the fetal head suture is close to or consistent with the transverse diameter of the pelvis, indicating a posterior position. The earlobe is located around 12 o'clock in the pelvic cavity. If the biparietal diameter has dropped to the level of the ischial spines or below, it is called a low posterior position; if the presenting part is higher, the fetal head suture is embedded in the transverse diameter of the pelvic inlet, indicating an uneven cephalopelvic obliquity. If the fetal head is inserted on one side of the top, the suture is oblique, it is called anterior uneven obliquity; if the suture is oblique forward, it is called posterior uneven obliquity. This type is often related to mild flatness of the pelvis or straight shape of the sacrum.

　　4. Ultrasound examination can be used to determine the position of the fetal head according to the biparietal diameter, facial and occipital position, and can clearly identify the position of the fetal head and make a timely diagnosis.

　　Patients with cephalic dystocia should eat foods rich in vitamin B, fresh vegetables, and fruits, try to eat less刺激性 food, and avoid eating too much salty, sweet, or greasy food, high-fat and high-calorie foods, and warm tonics.

　　The treatment principle for cephalic dystocia is vaginal delivery. If there is a high and straight posterior position, and artificial rupture of membranes and trial labor fail, cesarean section should be considered.

　　1. Before cesarean section, a comprehensive analysis of the medical history and prenatal examination data should be made to screen for pelvic contraction, severe cephalopelvic disproportion, or other obstetric complications. Women who are difficult to deliver vaginally should undergo elective cesarean section.

　　2. Trial labor can be performed under strict observation for women with relative cephalopelvic disproportion. Trial labor should be carried out when the fetal heart rate is normal and the uterine contraction is good. If the progress of labor during trial labor is smooth, it can continue until delivery is completed. If there is no obvious progress in labor for 2-4 hours during trial labor, cesarean section should be performed to complete delivery.

　　3. Oxytocin (Pitocin) is used for latent phase uterine contractions. First, allow the mother to rest and eat to increase energy, and diazepam (Valium) can be used for sedation if necessary. In addition, the mother can eat a fried egg with castor oil (30ml castor oil fried with 2 eggs), which can be taken on an empty stomach to enhance uterine contractions. If the above methods are ineffective, 500ml of 5% glucose solution + 5U of oxytocin can be slowly infused, and the infusion rate can be adjusted according to the uterine contraction. It is best to use a fetal heart and uterine contraction electronic monitor. If the active phase of uterine contractions is weak, the same method can be used to use oxytocin to enhance uterine contractions, closely observe whether the cervix dilates as expected, whether the fetal head descends as expected, and pay special attention to the shaping of the fetal head and the formation of the fetal head swelling. It is advisable to observe for 2 hours during this period, fully estimate the possibility of vaginal delivery. If there is no obvious progress in labor after strengthening uterine contractions, and the fetal head swelling becomes larger and larger, the use of oxytocin should be stopped, and cesarean section should be performed for safety.

　　4. For women with persistent posterior, transverse, or prolonged second stage of labor, according to the height of the presenting part, the size of the fetal head, and the degree of fetal distress, choose fetal head traction or forceps delivery. If the fetal head is in a high and straight position, anterior malposition, or facial position, and cannot be delivered vaginally, cesarean section should be performed.

　　5. Labor arrest often accompanies weak uterine contractions, so uterotonics should be administered postpartum to prevent bleeding and infection.