Persistent occipitoposterior position dystocia

　　Although the causes of persistent occiput posterior position are not yet fully clear, from the perspective of the interaction among the three major factors of the birth canal, fetus, and uterine contraction force, the formation of persistent occiput posterior position is not determined by a single factor, but often the result of the mutual influence and restriction of multiple factors. The main influencing factors include the following aspects:

　　1. Abnormal shape and size of the pelvis: It is an important cause of occiput posterior position, especially in the male and ape-shaped pelvis, where the anterior part of the pelvic inlet is narrow and the posterior part is wide. The wider occiput of the fetal head is prone to take the occiput posterior position into the pelvis; the middle pelvis is also narrow, making it difficult for the fetal head entering the pelvis in the occiput posterior position to perform internal rotation.

　　2. Incongruity between the pelvis and the fetal head size hinders the internal rotation of the fetal head: The incidence of pelvis-fetal incongruity in the persistent occiput posterior position group is significantly higher than that in the anterior occiput position group.

　　3. Poor fetal head flexion: The increased diameter of the fetal head passing through the birth canal often causes the diameter of the fetal head passing through the pelvis to be not proportional to the size of the pelvis, making the internal rotation and descent of the fetal head difficult, resulting in the persistent occiput posterior position. During anterior occiput delivery, the fetal head flexes well, passing through the birth canal with the occipitofrontal diameter (9.5cm); in the case of occiput posterior position, the fetal head flexion is poor, even without flexion, which may pass through the birth canal with the occipitoparietal diameter (11.3cm), increasing the fetal head diameter by 1.8cm. If the fetal head reaches the pelvic floor in a straight posterior position, the fetal head not only does not flex, but also slightly extends upwards, which Greenhill calls 'gooseneck', meaning to describe the situation where the fetal head extends upwards and the anterior fontanelle is exposed in the sacral straight posterior position. In this case, the increase in the fetal head diameter is more than 1.8cm. Therefore, the resistance encountered by the fetal head passing through the birth canal is much greater than that in the anterior occiput position, which is not conducive to the connection and rotation of the fetal head, nor is it conducive to the descent of the fetal head.

　　4. The causal relationship between persistent occiput posterior position and uterine contraction weakness: The internal rotation and descent of the fetal head both require uterine contraction force to complete. If the uterine contraction force is insufficient, it is difficult to promote the rotation of the fetal head. However, according to clinical data statistics, uterine contraction abnormalities are not the main cause of persistent occiput posterior position. But once uterine contraction abnormalities occur, it is even more difficult to overcome the occiput posterior position. Therefore, uterine contraction weakness is often the consequence of abnormal fetal position.

      The dystocia of persistent occiput posterior position mainly has two aspects of influence;

　　1. Effects on the Mother: Secondary uterine contraction weakness often occurs, leading to prolonged labor and increasing the risk of postpartum hemorrhage and intrauterine infection. The rate of instrumental delivery increases, and instrumental delivery is prone to cause soft tissue injury of the birth canal; at the same time, due to the long-term compression of the fetal head on the soft tissue of the birth canal, intestinal distension and urinary retention may occur, even leading to fistula of the reproductive tract; if the mother does not eat for a long time and does not receive nutritional and fluid supplementation through intravenous injection, it may also lead to electrolyte imbalance and acid-base imbalance.

　　2. Effects on the Fetus: Prolonged second stage of labor and instrumental delivery can increase the incidence of fetal distress, scalp edema and hematoma, intracranial hemorrhage, and neonatal asphyxia, thus increasing the perinatal mortality rate.

　　Common symptoms are as follows:

　　1. The fetal head connects later and has poor flexion after labor, due to the fact that the fetal presentation in the occipito-posterior position is not easy to adhere closely to the cervix and lower uterine segment, often leading to insufficient coordinated uterine contractions and slow cervical dilation.

　　2. Due to the continuous pressure of the occipital bone on the rectum from behind the pelvis, the产妇 feels anal prolapse and defecation, which leads to early use of abdominal pressure when the cervix has not fully dilated, and it is easy to cause edema of the anterior cervix and fatigue of the产妇, affecting the progress of labor.

　　3. The产妇 easily fatigue: It is related to the fact that the产妇 does not consciously push with abdominal pressure until the cervix is fully dilated.

　　4. Cervical edema, slow progress of labor. Persistent occipito-posterior position often leads to prolonged second stage of labor. It is necessary to find the occipito-posterior position early in the labor process so that timely treatment can be given to avoid prolonged labor.

　　5. If the fetal hair is seen at the vaginal orifice, and after several contractions and pushing, the fetal head does not continue to descend, it should be considered that it may be persistent occipito-posterior position.

　　6. Back pain: The产妇 soon after labor feels back pain, which appears with uterine contractions and becomes more severe as the labor progresses.

　　7. The产妇提前出现下屏: When the cervix is only dilated to 3-5cm in the early active phase, the产妇 has a prolapse sensation, which is due to the compression of the rectum by the fetal head at the pelvis entrance.

　　8. The anterior cervix often appears edematous: The cervix stops expanding at 8-9cm and is difficult to fully dilate.

　　9. Anal prolapse: Severe anal prolapse during the second stage of labor.

　　10. The labor process chart of persistent occipito-posterior position shows various abnormal conditions: According to reports, in 150 cases of persistent occipito-posterior position, 149 cases had different types of abnormalities except for 1 case with normal condition; ① The fetal head is blocked at the pelvis entrance, mostly manifested as delayed latent phase or (and) early active phase (cervical dilation 3-5cm) delayed or blocked cervical dilation; ② In the late active phase (cervical dilation 8-9cm), delayed or (and) blocked cervical dilation can be manifested as prolonged active phase or prolonged deceleration phase; ③ After the cervix is fully dilated, the descent of the fetal head is delayed or (and) blocked, causing prolonged second stage of labor.

　　11. Fetal presentation with a funnel-shaped pelvis: Fetal presentation with persistent occipito-posterior position is more likely to occur in funnel-shaped pelvises (including male and ape-shaped pelvises). In the early stage of clinical presentation, if the fetal head is found to be in a posterior position, one should be alert to the possibility of persistent occipito-posterior position.

　　Persistent occipito-posterior position is one of the common types of difficult labor, with common causes including pelvic abnormality, large fetus, poor flexion of the fetal head, and insufficient uterine contractions. Cesarean section and surgical delivery rates are high, and if not detected in time, it can lead to dystocia due to insufficient uterine contractions, postpartum hemorrhage, injury to the genital tract, puerperal infection, fetal distress, intracranial hemorrhage, perinatal death, and other maternal and fetal complications. Vaginal examination can be used to diagnose the condition. Apart from obvious cephalopelvic disproportion, all can be attempted. During labor, maintain good uterine power, closely observe the expansion of the cervix and the descent of the fetal head. If the fetal head cannot always connect, or if the fetal head connects but does not reach 2 or is blocked at the 2 level, cesarean section should be performed. When the occipito-posterior fetal head reaches 3 or below, it can be assisted by vaginal surgery.

　　I. Physical examination

　　1. Abdominal examination: The lower two-thirds of the maternal abdomen is occupied by the fetal limbs, the fetal back is偏 on the lateral posterior part of the mother, the fetal heartbeat can be heard on the right lower abdomen of the mother regardless of the occiput posterior left or right, but it is louder in the occiput posterior right position because the fetal left chest is close to the maternal anterior abdominal wall. The thing felt above the pubic symphysis in the lower abdomen is not the round and hard skull of the fetus, but the fetal chin. The position of the fetal chin determines the occiput posterior left or right. The position of the fetal chin in the lower right abdomen of the mother's abdomen is the occiput posterior left, and the position in the lower left abdomen is the occiput posterior right.

　　2. Anal examination: The posterior part of the pelvic cavity is empty in anal examination, the fetal head suture is located on the oblique or anteroposterior diameter of the pelvis, the posterior fontanelle of the occiput posterior position fetal head is located at the posterior part of the pelvis, and the anterior fontanelle is located at the anterior part of the pelvis. When the anterior fontanelle is felt in the right anterior part of the pelvis, it is the occiput posterior left, and vice versa for the occiput posterior right.

　　3. Combined application of anal examination and abdominal examination: In the early stage of labor, when the cervical os is only dilated to 3-5cm and the fetal head edema is not obvious, the fetal head suture can be understood through rectal examination. If the suture is on the left oblique diameter of the pelvis and the fetal chin is felt above the pubic symphysis on the right, it is suspected to be the occiput posterior left. If the suture is on the right oblique diameter of the pelvis and the chin is felt above the symphysis on the left, it is suspected to be the occiput posterior right.

　　4. Vaginal examination: It is a necessary means to confirm the occiput posterior position. To be a qualified obstetrician, the accuracy of vaginal examination in determining the fetal position should reach 80% to 90%. When the labor progress is abnormal, the cervical os dilates to 3cm or more, two fingers can be inserted into the uterine cavity to determine the fetal head position. When the cervical os is nearly fully open or fully open and soon after, the deformation and edema of the fetal head are not obvious, the accuracy can reach 90%.

　　II. Auxiliary examinations:It can be diagnosed clearly and dealt with in time, without the need for repeated anal and vaginal examinations.

　　1. Ultrasound imaging examination: It is necessary to combine with B-ultrasound examination when necessary, using ultrasound imaging to understand the position of the fetal head and face and the occiput, understand the changes in the position of the fetal head, with an accuracy of over 90%, and to deal with it in time, without the need to repeatedly perform vaginal examination.

　　2. X-ray diagnosis: The axis of the fetal head parietal opening direction (pointing to the occipital bone) is backward on the axial film, and the fetal spine is close to the maternal spine behind the mother in the lateral film, all indicating that the fetus is in the occiput posterior position. According to the anterior and posterior films, the fetal spine is on the left or right side of the mother, determining whether it is the occiput posterior left or right.

　　For the dietary care after a difficult labor with a persistent occiput posterior position, attention should be paid to:

　　In terms of diet, meals should be diverse, with a combination of coarse and fine grains, mixed with meat and vegetables, rich in protein, vitamins, and minerals, among which calcium and magnesium are very important.

　　Improve diet, eat more fruits, eggs, lean meat, and skin rich in vitamin C, E, and essential amino acids. These foods can promote blood circulation and improve the function of epidermal metabolism.

　　Avoid eating spicy foods such as chili, scallions, garlic, and other刺激性食物.

　　In the late stage of pregnancy (after 32 weeks), the occurrence of abnormal presentation and position of the fetus (abnormal presentation and position of the fetus generally refers to the abnormal position of the fetus in the uterine cavity after 30 weeks of pregnancy, which is more common in pregnant women with relaxed abdominal walls and multiparous women), is called 'malposition of the fetus'. It is also known as 'abnormal position of the fetus'. This disease is equivalent to fetal presentation and position abnormality in Western medicine, among which breech presentation and transverse lie are more common. Malposition of the fetus is one of the main factors causing dystocia, and can be detected and corrected early through regular antenatal examinations. The main cause is due to Qi deficiency or Qi stagnation, causing the fetus to lose harmony. 1. Qi deficiency: The pregnant woman is physically weak, with insufficient middle Qi, and has no strength to promote the adjustment of the fetus, leading to malposition of the fetus. 2. Qi stagnation: After pregnancy, the liver is depressed and Qi flow is blocked, the fetus cannot turn back, and thus the fetus is in malposition. In the process of differential diagnosis, while understanding the malposition of the fetus, attention should be paid to whether there is pelvic narrowness, deformation, and whether there is abnormal fetal development, so as to adopt appropriate treatment methods. The main treatment method is to invigorate Qi and nourish blood to turn the fetus for those with Qi deficiency, and to regulate Qi and smooth the fetus for those with Qi stagnation. At the same time, attention should be paid to the application of chest-knee position and acupuncture therapy in clinical practice. Women take blood as the root, and when the pregnant woman has abundant Qi and blood and smooth Qi flow, the fetus is in a normal position; if the pregnant woman is physically weak and lacks vital energy, has no strength to stabilize the fetus, or if the pregnant woman is emotionally depressed and Qi flow is blocked (Qi flow is blocked means that Qi is not flowing, and the concept of Qi can also be divided into many kinds in TCM syndrome differentiation. Qi flow is blocked, leading to stagnation and transformation...), it can also make it difficult for the fetus to return to the normal position.

　　The position of the fetus refers to the relationship between the specified part of the fetus's presentation and the anterior, posterior, left, and right sides of the maternal pelvis. The normal position of the fetus is mostly occiput anterior. After 30 weeks of pregnancy, if antenatal examination finds malpositions such as breech presentation, transverse lie, posterior occiput, and facial presentation, it is called 'malposition of the fetus' (malposition of fetus), among which breech presentation is the most common. If the malposition of the fetus is not corrected, it can cause dystocia during delivery.