Carpal tunnel syndrome (CTS) is a syndrome in which the median nerve is compressed within the carpal tunnel, causing pain and numbness in the area of its innervation. CTS is more common in middle-aged women than in men, and is three to four times more common in the United States. Neurologists consider CTS in pregnancy to be rare. In recent years, CTS has been recognized as the most common neurological entrapment syndrome in pregnancy [1]. Due to inconsistent research methods and diagnostic criteria, the incidence of CTS in pregnancy has been inconsistently reported in the literature, ranging from about 1% to 60%. Due to the lack of sufficient knowledge about CTS in pregnancy, it is often misdiagnosed or missed in clinical work. CTS in pregnancy is most often seen in older women at the end of their first pregnancy and is associated with hand or generalized edema, mostly bilateral or unilateral in the right hand. It is not related to the number of pregnancies or the use of the hands. The onset of the disease is concentrated between the 7th month of gestation and the 3rd month after delivery. Most of the literature suggests that carpal tunnel syndrome in pregnancy is usually self-limiting, with most patients’ symptoms resolving after delivery. Only a few patients with severe symptoms and ineffective conservative treatment can be considered for surgery. The carpal tunnel is a tough and inelastic fibrous sheath of bone, consisting of the bottom and both walls of the carpal bone, which is covered by the transverse carpal ligament into a bone-fiber tunnel. Any cause of pressure increase in the carpal tunnel, such as exogenous compression, the lumen itself becomes smaller and the lumen contents increase in size, can cause the median nerve to be compressed, thus manifesting a set of corresponding symptoms and signs. There are several causes of CTS: (1) mechanical factors. Fractures and dislocations of the wrist (fractures of the lower radius, carpal fractures, and perilunate carpal dislocations) can cause the posterior or lateral walls of the carpal tunnel to protrude into the lumen, narrowing the carpal tunnel, and thickening the transverse carpal ligament due to scar formation after trauma; long-term overexertion of the wrist, such as carpenters, cooks, and computer users; related to the sleeping position, lateral lying can cause the wrist to hyperextend or hyperflex, increasing the pressure in the carpal tunnel [2]; and lipomas, hemangiomas, neuromas, and nerve tumors in the carpal tunnel. The carpal tunnel can also be affected by lipomas, hemangiomas, neuromas, nerve sheath carcinomas, tendon sheath cysts, gout nodules and other occupying lesions, which can reduce the volume of the carpal tunnel, obstruct blood and lymphatic flow, and increase the pressure and cause compression of the median nerve. (2) Inflammatory factors. Infection such as tenosynovitis, bursitis, tendonitis, etc., inflammatory exudate wrapping and surrounding tissue inflammatory edema, resulting in local tissue adhesions; carpal tunnel tissue damage, carpal tunnel pressure increase; at the same time, inflammatory exudate mechanization of the carpal tunnel vascular, nerve and tendon extensive adhesions restricted activity. (3) Endocrine factors. Obesity, diabetes, thyroid dysfunction, amyloidosis or Reynaud’s disease, pregnancy, lactation, menopause and other endocrine metabolic disorders. In recent years, many scholars have studied the etiology of CTS in pregnancy. It is believed that CTS during pregnancy may be related to the following factors: (1) edema. The systemic blood volume starts to increase from the 6th week of gestation and reaches a peak at 32-34 weeks of gestation, which decreases the plasma osmolarity and causes tissue edema; the peripheral blood vessels dilate after the middle and late pregnancy, and the vascular flow in the hand is 7 times higher than that in non-pregnancy; there is a large amount of fluid leakage around the tendon sheath, the median nerve envelope and the blood vessels and lymphatic tissue around the carpal tunnel in late pregnancy. As a result of generalized edema, the tendons, tendon sheaths and connective tissues around the nerve are swollen, while the volume of the carpal tunnel is fixed, and the median nerve, which is confined in the carpal tunnel, is compressed, resulting in symptoms and signs in the distribution area of the median nerve. (2) Hormones. After pregnancy, the hormones in the body increase, especially estrogen, which can easily cause water and sodium retention, thus causing generalized edema. Studies have shown that some women will experience CTS after taking birth control pills with estrogen as the main ingredient. late in pregnancy, the concentration of estrogen in the blood reaches its peak, and drops sharply after delivery. In addition, the secretion of prolactin increases sharply after delivery, and continued breastfeeding maintains the blood concentration of prolactin, which has a similar effect to that of antidiuretic hormone, leading to the conclusion that water and sodium retention is one of the causes. In addition, some scholars believe that relaxin in the body during pregnancy relaxes the transverse carpal ligament, and factors such as the age of the pregnant woman and pre-eclampsia may be related to CTS during pregnancy. It is also believed that gout, rheumatism and tuberculosis are susceptibility factors. 2, clinical manifestations and classification of CTS typical clinical symptoms are numbness, pain and decreased grip strength of the hand. Early symptoms may not be obvious, often manifesting as intermittent sensory dysfunction of the fingertips, and some patients may recover spontaneously. In some patients, the symptoms may continue to worsen and develop from intermittent impairment to persistent numbness and pain, which often intensifies at night and is relieved by activity, thus affecting sleep. Sometimes the pain may radiate to the forearm. These symptoms are mainly in the index finger, followed by the middle finger, thumb and ring finger, and do not usually involve the little finger. In the later stage, a few patients develop neurotrophic disorders, which are characterized by atrophy and paralysis of the masseter muscle (thumb flexor and thumb palmaris) and reduced muscle strength, and in severe cases, cyanosis of the thumb and index finger, finger tip necrosis or atrophic ulcers. It occurs in late pregnancy and is more common in young primiparous women, and often exists bilaterally. Classification of CTS: (1) Mild. Intermittent sensory abnormalities. (2) Moderate. Frequent sensory abnormalities. (3)Severe. Persistent sensory abnormalities or atrophy, paralysis and muscle weakness of the masseter muscle (thumb flexor shortus, thumb opposite palmaris) [3]. 3, diagnosis The main diagnostic bases of CTS at present are: (1) clinical manifestations. Pain, abnormal sensation or sensory deficit in the affected median nerve innervation area. The wrist tendons and muscles appear stiff, striated or nodular, with localized pressure pain and swelling of the wrist joint. Late stage thumb can be seen as muscle weakness, muscle atrophy, and decreased local sensation by pinprick. (2) Tourniquet pressure test. A tourniquet is tied to the upper arm of the affected limb and inflated for about 1 min, which is positive if the finger shows numbness. (3) Percussion test (Tinel’s test). If there is numbness or radiating electric shock-like tingling in the fingers, it is positive, with 99% specificity and 64% sensitivity. (4) Wrist flexion test (Phalen’s test). If pain or sensory abnormality occurs within 1 min of flexing the wrist, it is a positive sign with a specificity of 95% and sensitivity of 75%. (5) Neuroelectromyography. The electromyography of the interosseous muscle and the conduction velocity of the median nerve of the wrist and finger have nerve damage signs. The main parameters include mixed muscle action potential, sensory nerve action potential, and nerve conduction velocity, and the results showed that nerve conduction began to decrease at 22 weeks of gestation, reached the lowest point at 24-26 weeks, and reached the normal baseline level at 20 weeks after delivery [4]. It has been suggested that CTS can be diagnosed by a positive Tinel’s test, a positive Phalen’s test or an abnormal EMG on the basis of clinical manifestations. In 2000-2001, a multicenter clinical study conducted by Italian scholars on CTS in pregnancy combined found that 62% of pregnant women were diagnosed with CTS by clinical symptoms and 43% by neurophysiological methods. In a multicenter clinical study conducted by Italian scholars in 2000-2001, it was found that 62% of pregnant women were diagnosed with CTS by clinical symptoms and 43% by neurophysiological methods. There are no uniform criteria in the literature to evaluate the treatment of CTS in pregnancy. In view of the fact that most of the literature reports that CTS in pregnancy can disappear after delivery and has self-healing characteristics, the disease is mainly treated conservatively [5]. If conservative treatment is ineffective or the symptoms worsen, local closure or surgery can be considered. 41, conservative treatment (1) wrist exercise: its mechanism may be to increase venous return, reduce edema, suitable for early mild patients. (2) Wrist splint: when the wrist is in neutral position, the pressure in the carpal tunnel is the lowest. It can be used to fix the wrist in neutral position, which can make local rest and prevent wrist flexion. It is suitable for mild or moderate CTS, and it is effective for patients who wake up at night due to repeated pain. (3) Physiotherapy: It mainly increases blood circulation and reduces local irritation. In addition, the application of dehydrating diuretics, reduce salt intake, to reduce or eliminate tissue edema also has a certain effect; taking vitamin B12 can nourish the nerve; taking non-steroidal drugs may also have some effect. 42, carpal tunnel closure Currently, the commonly used method is the carpal tunnel injection of steroid hormones such as steroids, should be careful not to inject drugs into the median nerve, otherwise it may produce chemical inflammatory reaction, but aggravate the symptoms. Patients with a short course and mild CTS can usually receive better results. It is more suitable for patients with CTS in late pregnancy. NSAIDs may be effective in patients with CTS with acute inflammation, but the treatment effect on most patients with CTS in pregnancy is very small. In the literature, it has been reported that 0.5%-32% of patients with CTS in pregnancy underwent surgical decompression [6]. Stahl et al [7] concluded that: CTS-related symptoms in early or mid-pregnancy; previous history of CTS; positive Phalen test and abnormal two-point discrimination sensation should be treated surgically as early as possible, otherwise patients must eventually undergo surgery during pregnancy or postpartum. Otherwise, the patient must eventually undergo surgery during pregnancy or after delivery. The surgery is performed under local anesthesia and has no adverse effects on the pregnant woman or the fetus. The operation is the same as general CTS, and the results are generally satisfactory, while endoscopic surgery is less invasive than open surgery, with less postoperative pain and faster recovery. The appropriate time for surgery is difficult to determine, but where there is myasthenia gravis, or by other treatment has little effect, or 6 months after delivery, the symptoms do not improve can be considered for surgery. The prognosis is that the symptoms associated with CTS will disappear naturally with the end of delivery. In recent years, many scholars have conducted follow-up studies on CTS in pregnancy. A Turkish study concluded that only 4% of patients had symptoms one year after delivery; however, an Italian multicenter study showed that 54% of mothers still had symptoms one year after delivery. In a 1-year follow-up study, it was concluded that postpartum symptoms improved significantly in patients with CTS in pregnancy, but more than 50% of patients still had symptoms related to CTS and had insignificant neuromyographic changes; the earlier the onset of clinical symptoms or significant weight gain during pregnancy, the worse the prognosis, In a prospective study, 45 cases of CTS in pregnancy were studied and 90 cases of primary CTS (non-pregnant) were used as a control group. The results showed that the clinical symptoms of CTS in pregnancy were short-lived and mild, with more involvement of the hands and less severe neuromyographic changes, This suggests that the prognosis of CTS in pregnancy is better than that of primary CTS.