Amniotic Band Syndrome

　　The etiology of amniotic band syndrome is not yet fully understood. There are three hypotheses about the etiology as follows:

　　First, etiological hypothesis

　　1. Theory of external causes

　　In the early stage of pregnancy, the amniotic cavity ruptures for unknown reasons while the chorion is intact. The fetus reaches the chorionic cavity through the amniotic cavity rupture. Due to the good permeability of the chorion, amniotic fluid exudes, leading to transient oligohydramnios, and the fetus is close to the chorion. The chorionic tissue has the ability to proliferate and infiltrate, and after contacting various tissues of the fetus, it destroys the contacted tissues, resulting in malformations in the corresponding areas.

　　In the theory of external causes, it must be emphasized that the rupture of the amniotic cavity occurs in the early, middle, and late stages of pregnancy, especially the rupture of the amniotic membrane in the late stage of pregnancy, which usually will not cause amniotic band syndrome. Amniocentesis in the late stage of pregnancy, the amniotic cavity has a puncture hole left due to the puncture, but it has been confirmed that amniocentesis at this time does not cause amniotic band syndrome.

　　2. Endogenous theory

　　Although amniotic band syndrome is related to the amniotic band, no direct evidence has been found that the amniotic band causes amputation or malformation, so some scholars believe that the fundamental cause of amniotic band syndrome is the abnormality of genetic material, that is, the theory of genetic material deficiency.

　　3. Vascular theory

　　Amniotic band syndrome often complicates complex visceral malformations, and it is difficult to explain multiple complex visceral malformations with the theory of amniotic rupture.

　　(II) Pathogenesis

　　1. The fibrous bands of the chorionic membrane wrapping the fetal limbs can lead to fetal malformations and skin defects; the fibrous bands adhering to the defective skin can lead to abdominal cleft or encephalocele and other malformations; the fetus biting and swallowing the amniotic band can lead to asymmetric cleft lip, cleft palate, or digestive tract atresia.

　　2. The mechanical compression or constraint of the amniotic band should also be one of the mechanisms of amniotic band syndrome. It should be emphasized that the time when the amniotic band affects the fetus may not be limited to the early stage of pregnancy, but should also play a role in the middle and late stages of pregnancy, because after the amniotic band ligation surgery in the middle and late stages of pregnancy, the affected limbs can recover normal development.

　　3. In the early stages of embryogenesis, due to abnormal genetic material, the intrinsic linear germ cells are disordered or the connective tissue of the limbs develops abnormally, leading to various malformations in the end.

　　In histological studies, it was found that vascular rupture and hemorrhage occur earlier than malformations such as amniotic band-induced limb amputation and abdominal cleft. Therefore, some scholars have proposed the following hypothesis: The mesenchymal cells and epithelial cells of the superficial vessels of the embryonic amniotic membrane are damaged, the embryonic ectoderm breaks, and secondary limb amputation, encephalocele, and malformations of fingers (toes), feet (hands), etc. occur.

　　In the early pregnancy of amniotic band syndrome patients, the amniotic membrane breaks for unknown reasons while the chorion remains intact. The fetus reaches the chorionic cavity through the amniotic membrane break due to the good permeability of the chorion. There is transient oligohydramnios due to the leakage of amniotic fluid, and the fetus is close to the chorion. The chorion tissue has the ability to proliferate and infiltrate. After contacting with various tissues of the fetus, it destroys the contacted tissues, resulting in malformations in the corresponding areas.

　　Amniotic band syndrome has the characteristics of low incidence and sporadic, with no specific clinical symptoms and signs in the early pregnancy. There are no obvious signs of oligohydramnios and no abnormal rate of uterine growth in the early and mid-pregnancy.

　　Due to the different locations and degrees of fetal malformation, the treatment methods are also different. For small adhesions and lymphedema of fingers and toes, the prognosis is usually good; for limb amputation deformities, it is more serious; and multiple malformations often lead to death. In recent years, there have been more reports on the use of fetal镜 to release the amniotic bands around the limbs, which can lead to normal development of the limbs. This suggests that if early diagnosis can be made, some fetal malformations in amniotic band syndrome may be corrected through intrauterine surgery. However, the focus of ABS is on prevention. It should be reminded that pregnant women should do a good job of perinatal health care, try to prevent intrauterine infection, and regular ultrasound examinations should be conducted if there is trauma or medical diagnosis of amniocentesis. If routine ultrasound examinations can be performed during the midpregnancy period, and the identification of this disease is strengthened, early diagnosis and treatment will be of great significance for improving the quality of perinatal infants.

　　The diagnosis of amniotic band syndrome mainly relies on imaging examinations, including B-ultrasound and magnetic resonance technology (MRI).

　　1, B-ultrasound

　　This is an important method for diagnosing amniotic band syndrome. During the process of diagnosing amniotic band syndrome by B-ultrasound, the following points should be noted.

　　(1) The diagnosis of amniotic band syndrome by B-ultrasound is first to find various fetal malformations under B-ultrasound, often accompanied by oligohydramnios.

　　(2) Carefully examine, irregular strip-like echoes are found in the site of fetal malformation or other sites, with attachment points located on the amniotic membrane or fetal body.

　　(3) Further clarify the type of fetal malformation with B-ultrasound examination.

　　2, Magnetic Resonance Technology

　　MRI technology has been successfully applied in obstetrics. The greatest advantage compared to B-ultrasound is the high image clarity, good spatial resolution of organs, and high resolution of tissue structures, with minimal influence from scan thickness, air, and bony organs. The clarity of imaging of the uterus, placenta, amniotic fluid, and various organs of the fetus, as well as the non-reproductive organs and tissues around the uterus, is significantly better than that of B-ultrasound. MRI scanning is not affected by the obesity of pregnant women or the enlarged uterus during pregnancy. In these two cases, the structure at the distal end of the B-ultrasound probe is not clearly displayed; MRI technology is not affected by intestinal gas and bony parts of the pelvis. The application of MRI technology in obstetrics in China is relatively rare, while it has been widely used abroad and is still considered as an auxiliary technology to B-ultrasound. There have been cases abroad where MRI technology has successfully diagnosed amniotic band syndrome. It is recommended that all pregnant women with suspected or detected fetal malformations must undergo MRI examination.

　　Dietary regulation has little effect on the prevention and alleviation of amniotic band syndrome, but during pregnancy, patients should also pay attention to a balanced diet, and can eat more vegetables. However, although spinach and kelp are rich in nutrients, they should be eaten in moderation because spinach contains a large amount of folic acid, which affects the absorption of zinc and calcium, and excessive consumption of kelp can lead to excessive iodine, which can cause developmental disorders of the fetus's thyroid gland. Unripe tomatoes and vegetables that have been stored for too long, such as potatoes, can affect the health of pregnant women and the fetus. Therefore, pregnant women can only eat cooked fresh vegetables, and they should not eat foods that are too salty, too spicy, burnt, or fried.

　　After the diagnosis of amniotic band syndrome, a treatment plan needs to be formulated. The formulation of the treatment plan is constrained by the gestational age, the organ, type, and degree of malformation, the long-term and short-term impact of the malformation on the growth and development of the fetus, the value of the fetus, the level of neonatal or fetal medicine, especially fetal surgery, and many other conditions.

　　1. Let nature take its course, and recover spontaneously after delivery. This is mainly for mild malformations with little impact on the fetus and neonate.

　　2. No treatment is given during pregnancy; treatment is carried out after full-term delivery.

　　3. Induction of labor is mainly aimed at cases where the fetus is dead, or there are severe or important organ malformations that have a significant impact on the long-term and short-term development and growth of the fetus, and the family requests termination of pregnancy, or the neonatal or fetal medical level is poor.

　　4. Intrauterine treatment refers to intrauterine surgery. Fetal medicine, especially fetal surgery, is an emerging science that has developed in recent years. It has already successfully treated various fetal malformations or structural abnormalities with intrauterine treatment and is currently tackling the intrauterine treatment of fetal heart abnormalities. The most common surgical procedure for amniotic band syndrome is amniotic band adhesion release, which can achieve good clinical effects.