Weak uterine contractions

　　Whether primary or secondary, once weak uterine contractions occur, the cause should be sought first, such as malpresentation and abnormal fetal position, and understand the expansion of the cervix and the descent of the presenting part of the fetus. Weak uterine contractions are often caused by a combination of several factors, and the common causes are as follows.

　　1. Malpresentation or abnormal fetal positionThe descent of the presenting part of the fetus is obstructed, and it cannot adhere to the lower segment of the uterus and the cervix. Therefore, it cannot cause reflex uterine contractions, leading to secondary weak uterine contractions.

　　2. Uterine factorsUterine hypoplasia, uterine malformations (such as bicornuate uterus), excessive expansion of the uterine wall (such as twins, macrosomia, polyhydramnios), fibrosis of the uterine muscle fibers in multiparas, or uterine fibroids, etc., can all cause weak uterine contractions.

　　3. Psychological factorsFor primiparas (primipara) [especially elderly primiparas over 35 years old], excessive mental tension can disrupt the function of the cerebral cortex, lead to insufficient sleep, reduced food intake during labor, and excessive physical exhaustion, all of which can cause weak uterine contractions.

　　4. Endocrine disordersAfter childbirth, the secretion of estrogen, oxytocin, prostaglandins, acetylcholine, and other substances in the mother's body is insufficient, the decline of孕激素is slow, and the sensitivity of the uterus to acetylcholine decreases, all of which can affect the excitation threshold of the uterine muscle, leading to weak uterine contractions.

　　5, Drug influence: Improper use of large doses of sedatives and analgesics after labor, such as morphine, chlorpromazine, pentazocine, barbiturates, etc., can suppress uterine contractions.

　　The incidence of this disease is high in patients with malpresentation, malposition of the pelvis, multiple pregnancies, twins, polyhydramnios, and other local uterine factors. It also occurs in patients with nervous tension. If the antenatal and labor process can be handled in a timely and correct manner, it can reduce the occurrence of uterine contraction weakness. Uterine contraction weakness can lead to delayed or stagnation of the descent of the fetal head, causing dystocia. It is prone to fetal distress in utero, neonatal asphyxia, or intracranial hemorrhage and other complications.

　　Uterine contraction weakness refers to the situation where, during labor, the female's uterus has a problem with contractions, causing the cervix to remain dilated while the fetus wants to be born. This condition, if it persists for a long time, can lead to fetal asphyxia. Therefore, pregnant women should first understand the common symptoms of uterine contraction weakness so that they can effectively prevent the disease. The common symptoms are as follows:

　　1, Coordination of uterine contractions (hypotonic uterine contractions)

　　Uterine contractions have normal rhythm, symmetry, and polarity, but the contraction force is weak, the uterine cavity pressure is low (＜2.0kPa), the duration is short, the interval is long and irregular, and the contractions are ＜2 times/10 minutes. When the uterus reaches the peak of contraction, the uterine body does not bulge and harden, and the muscle wall of the uterine bottom can still appear concave when pressed with fingers. Labor may be prolonged or stagnant, and the fetal impact is not significant due to the low uterine cavity tension.

　　2, Incoordination of uterine contractions (hypertonic uterine contractions)

　　The inversion of the polarity of uterine contractions, where the contractions do not originate from both corners of the uterus, but from one or more places in the uterus. The rhythm is not coordinated, the fundus is not strong during contractions, but the middle or lower segment is strong, and the uterine wall cannot completely relax during the intercontraction period, which is manifested as the lack of coordination of uterine contractions. This kind of contraction cannot dilate the cervix, cannot lower the presenting part of the fetus, and is an ineffective contraction. The patient may feel continuous pain in the lower abdomen, refuse to be pressed, be restless, dehydrate, electrolyte disorder, intestinal distension, urinary retention, and fetal-placental circulation disorder, which may lead to fetal distress in utero. There may be tenderness in the lower abdomen, unclear position of the fetus, irregular fetal heart rate, slow or no dilation of the cervix, delayed or stagnation of the descent of the presenting part, prolongation of labor.

　　3, Abnormality of labor distension

　　The weakness of uterine contractions can lead to abnormal labor curves, which can be divided into the following 7 types.

　　1, Prolongation of the latent phase:From the onset of regular uterine contractions to the expansion of the cervix to 3cm is called the latent phase. The normal duration of the latent phase for a primipara is about 8 hours, with the maximum limit of 16 hours. If it exceeds 16 hours, it is called the prolongation of the latent phase.

　　2, Prolongation of the active phase:From the expansion of the cervix to 3cm to the full opening of the cervix is called the active phase. The normal duration of the active phase for a primipara is about 4 hours, with the maximum limit of 8 hours. If it exceeds 8 hours, it is called the prolongation of the active phase.

　　3, Stagnation of the active phase:After entering the active phase, the cervix no longer expands for more than 2 hours, which is called the stagnation of the active phase.

　　4, Extended second stage of labor:If a primipara exceeds 2 hours in the second stage of labor and a multipara exceeds 1 hour without delivery, it is called an extended second stage of labor.

　　5, Second stage of labor arrest:If there is no progress in fetal head descent for 1 hour during the second stage of labor, it is called second stage of labor arrest.

　　6, Fetal head descent delay:If the fetal head descent rate is less than 1cm per hour from the late active phase to the 9-10cm dilatation of the cervix, it is called fetal head descent delay.

　　7, Fetal head descent arrest:If the fetal head remains in the same place without descending for more than 1 hour, it is called fetal head descent arrest.

　　Prenatal education should be provided to pregnant women to relieve their concerns and fear, so that they understand that pregnancy and childbirth are physiological processes. Currently, in China and other countries, there are leisure waiting rooms (allowing their partners and family members to accompany them) and family-style wards, which help to eliminate the anxiety of women in labor, enhance their confidence, and can prevent uterine atony caused by excessive mental stress. Encourage pregnant women to eat more during labor, and nutrition can be supplemented intravenously when necessary. Avoid excessive use of sedatives, check for cephalopelvic disproportion, and other measures are effective in preventing uterine atony. Pay attention to emptying the rectum and bladder in a timely manner, and warm soap water enema and catheterization can be performed when necessary.

　　The diagnosis of uterine atony relies not only on clinical manifestations and signs but also on routine obstetric and gynecological examinations performed by the patient, such as gynecological ultrasound, uterine examination, bimanual examination, vaginal examination, and cervical examination.

　　Women with uterine atony can eat semi-liquid foods such as noodles, wontons, millet red bean porridge, steamed buns, bread, soda crackers, braised tofu, steamed fish, and braised fresh vegetable ends. Women should eat easily digestible foods that promote defecation, such as vegetables, seaweed, pork blood, carrots, etc. Eating more fibrous foods such as fruits, brown rice, whole grains, and beans can stabilize blood sugar and reduce blood cholesterol.

　　Strengthening uterine contractions is the fastest and most effective method for stopping bleeding due to uterine atony. Once postpartum hemorrhage occurs, it is necessary to immediately massage the fundus, open venous channels, empty the bladder, and perform a vaginal examination to clarify the cause of bleeding, and prepare for抢救失血性休克. Drug therapy is首选, and surgery is performed when necessary. Commonly used drugs include oxytocin, ergot derivatives, prostaglandins, and recombinant activated factor VII. Compression method is often used when massage and drug therapy are ineffective or in emergency situations. When conservative treatment is ineffective, conservative surgical treatment is generally首选 for women who urgently hope to preserve their reproductive function, including pelvic vascular ligation (uterine artery ligation and internal iliac artery ligation), B-Lynch surgical suture method, and selective arterial angiography embolization. Among them, the B-Lynch surgical suture method is a suture method for controlling postpartum hemorrhage first reported by Milton Keynes Hospital in the UK in 1993. By adding pressure to the uterus with sutures on the anterior and posterior uterine walls, it can effectively treat postpartum hemorrhage caused by uterine atony. Different treatment methods are adopted for different clinical manifestations of uterine atony.

　　1. Uterine contraction insufficiency due to coordination

　　Whether primary or secondary, once there is uterine contraction insufficiency, the cause should be sought first, including malpresentation of the pelvis and abnormal fetal position, and the situation of cervical dilation and descent of the presenting part of the fetus should be understood. If there is malpresentation of the pelvis and it is estimated that it cannot be delivered vaginally, cesarean section should be performed in time. If there is no malpresentation of the pelvis and abnormal fetal position, and it is estimated that it can be delivered vaginally, measures to strengthen uterine contraction should be considered.

　　1. General treatment

　　Relieve mental tension, rest more, and encourage more eating. For those who cannot eat, nutrition can be supplemented intravenously by adding 2g of vitamin C to 500 to 1000ml of 10% glucose solution. For those with acidosis, 5% sodium bicarbonate should be supplemented. For those with hypokalemia, potassium chloride should be administered slowly by intravenous infusion. For women who are overly tired, 10mg of diazepam can be administered slowly by intravenous injection or 100mg of pethidine can be injected intramuscularly. After a period of time, this can make the uterine contraction stronger. For those who have difficulty in urination, induction methods should be tried first, and if ineffective, catheterization should be performed because emptying the bladder can widen the birth canal and has the effect of promoting uterine contraction. For primiparas with insufficient cervical dilation of less than 3cm and intact membranes, warm soap water enema should be administered to promote peristalsis, expel feces and gas, and stimulate uterine contraction.

　　2. Strengthening uterine contraction

　　After general treatment, if the uterine contraction is still weak, diagnosed as uterine contraction insufficiency, and there is no obvious progress in labor, the lower segment method can be used to strengthen uterine contraction.

　　(1) Artificial rupture of membranesFor women with cervical dilation of 3cm or more, no malpresentation of the pelvis and fetus, and the fetal head has engaged, artificial rupture of membranes can be performed. After membrane rupture, the fetal head directly adheres to the lower segment of the uterus and the cervix, causing reflex uterine contraction and accelerating the progress of labor. Some scholars advocate that artificial rupture of membranes can also be performed for women with unengaged fetal heads, believing that membrane rupture can promote the descent of the fetal head into the pelvis. It is necessary to check for umbilical prolapse during membrane rupture, and membrane rupture should be performed during the intercontraction period. After membrane rupture, the operator's fingers should remain in the vagina, and after 1 to 2 contractions, the operator should remove the fingers after the fetal head has entered the pelvis.

　　(2) Intravenous bolus injection of diazepam (valium)Diazepam can relax the uterine smooth muscle, soften the cervix, and promote cervical dilation, which is suitable for slow cervical dilation and cervical edema. The common dose is 10mg intravenous bolus injection, which can be repeated every 2 to 6 hours, and the effect is better when combined with oxytocin.

　　(3) Application of prostaglandin (prostaglandin, PG)Prostaglandin E2 and F2α both have the effect of promoting uterine contraction. The administration routes include oral, intravenous infusion, and local application (placed in the posterior fornix of the vagina). Intravenous infusion of PGE2 at 0.5μg/min and PGF2α at 5μg/min can usually maintain effective uterine contraction. If the uterine contraction is still not strong after half an hour, the dose can be increased appropriately, with the maximum dose of 20μg/min. The side effects of prostaglandins include excessive uterine contraction, nausea, vomiting, headache, tachycardia, blurred vision, and superficial thrombophlebitis, so they should be used with caution.

　　(4) Oxytocin Intravenous Infusion: Suitable for patients with inadequate coordination of uterine contraction, good fetal heart rate, normal fetal position, and appropriate pelvis and head size. During the process of oxytocin infusion, a person should be assigned to observe uterine contraction, listen to fetal heart rate, and measure blood pressure. If uterine contraction lasts for more than 1 minute or there is a change in fetal heart rate, the infusion should be stopped immediately. The half-life of oxytocin in maternal blood is 2-3 minutes, and it can quickly improve after stopping the medication. Sedatives can be added if necessary to inhibit its effect. If blood pressure increases, the infusion rate should be slowed down. Due to the antidiuretic effect of oxytocin, the reabsorption of water increases, which can cause oliguria, and water intoxication should be警惕.

　　If the labor process still does not progress or signs of fetal distress appear after the above treatment, cesarean section should be performed in a timely manner. If there is no malpresentation during the second stage of labor and uterine contraction is weak, uterine contraction should be strengthened, and oxytocin infusion should be given intravenously to promote the progress of labor. If the biparietal diameter of the fetal head has passed through the pelvic inlet, wait for natural childbirth, or perform perineal lateral incision, perform fetal head traction or forceps delivery. If the fetal head has not engaged or accompanied by signs of fetal distress, cesarean section should be performed. After the situation improves, prevent postpartum hemorrhage and infection.

　　II. Inadequate Coordination of Uterine Contraction

　　The principle of treatment is to regulate uterine contraction and restore the polarity of uterine contraction. Administer strong sedative Demerol 100mg or Morphine 10-15mg intramuscularly to allow the mother to rest fully, and most of them can recover to coordinated uterine contraction after waking up. It is strictly forbidden to use oxytocin before the uterine contraction is restored to coordination. If the above treatment does not correct the dyscoordinated uterine contraction, or accompanied by signs of fetal distress, or accompanied by malpresentation, cesarean section should be performed. If the dyscoordinated uterine contraction has been controlled, but the uterine contraction is still weak, then the method of strengthening uterine contraction during the period of weak coordinated uterine contraction can be adopted.