What Is Amniotic Band Syndrome?

Amniotic band syndrome has many names, such as congenital annular adhesion cobweb syndrome, etc., which refers to the rupture of part of the amniotic membrane to produce fiber bundles or fibrous sheaths, which cause the embryo or fetus to adhere to the amniotic band, restrain, oppress, entangle the fetus, make the fetus Affected organs appear divided or deformed. Common affected areas are the head, trunk, and limbs. There are various types of malformations, ranging from small deformities of the hands, feet or fingers (toes) to multiple complex deformities of the whole body.

Basic Information

nickname: Congenital annular adhesion cobweb syndrome
English name: amniotic band syndrome
Visiting department: Obstetrics and Gynecology

Common locations: Fetal head, trunk and limbs
Common symptoms: Embryo or fetus adheres to the amnion band, restrains, oppresses, entangles the fetus, causing the affected organs to divide or develop abnormalities

Causes of amniotic band syndrome

The cause of amniotic band syndrome is not fully understood. There are the following hypotheses about the cause:

External cause theory

Unexplained amniotic membrane rupture in early pregnancy, but the chorion is intact, and the fetus reaches the chorionic cavity through the rupture of the amniotic membrane. Because the chorion is more permeable, the amniotic fluid is extravasated, the transient amniotic fluid is too little, and the fetus is close to the chorion. The chorionic tissue has the ability to proliferate and infiltrate. After contacting various tissues of the fetus, the contacted tissue is destroyed, and then deformities of the corresponding parts occur.

In recent years, the progress of fetal medicine, especially fetal surgery, has been successfully performed for the treatment of amniotic band syndrome with intrauterine amniotic band release, and the affected limbs can be freed from the restriction of the amniotic band and resume normal development.

2. Internal cause theory

Although amniotic band syndrome is associated with amniotic bands, no direct evidence of amniotic bands causing amputations or deformities has been found. Some scholars believe that the root cause of amniotic band syndrome is the abnormality of genetic material, that is, the theory of lack of genetic material.

3. Vascularism

Amniotic band syndrome is often associated with complex visceral deformities. A variety of complex visceral deformities are difficult to explain with the theory of amniotic membrane rupture in rats without amniotic membrane rupture by using vasoactive substances to establish animal models of amniotic band syndrome.

Clinical manifestations of amniotic band syndrome

There were no special clinical symptoms and signs during pregnancy, no significant decrease in amniotic fluid, and normal uterine growth rate.

Amniotic band syndrome test

Amniotic band syndrome is diagnosed mainly by imaging studies, including B-mode ultrasound and magnetic resonance imaging (MRI).

1.B ultrasound

This is an important method for diagnosing amniotic band syndrome. In the process of B-ultrasound diagnosis of amniotic band syndrome, the following points must be paid attention to:

(1) B-ultrasound diagnosis Amniotic band syndrome First, various fetal malformations were found under B-ultrasound, often with oligohydramnios.

(2) Carefully inspect the fetal malformation or other parts for irregular band-like echoes, and the attachment point is located on the amnion or fetal body.

(3) B-ultrasound Examine the types of fetal malformations. Limb parts Amputation of limbs, lymphedema, finger (toe), raised skin, deformed foot. Skull site Asymmetric encephalocele, anencephaly, and lack of skull. Facial parts Cleft lip and palate, abnormal nasal development, asymmetrical microcephaly. Thoracic rib fracture, abnormal heart. spine Scoliosis, spina bifida. abdominal wall, abdominal fissure, umbilical bulge and bladder eversion. vulva genitalia is unclear, anal atresia. B-ultrasound diagnosis is characterized by multiple occurrences, asymmetry and complexity.

2. Magnetic resonance technology

MRI technology has been successfully used in obstetrics. The biggest advantages compared with B-mode ultrasound are high imaging clarity, good spatial structure resolution and tissue structure resolution. Affected by scanning thickness including gas, bone and organs. The imaging clarity of MRI on various organs of the uterus, placenta, amniotic fluid, and fetus, as well as the organs and tissues of the non-reproductive system around the uterus, is significantly better than that of ultrasound. MRI scans are not affected by maternal obesity and enlarged pregnant uterus. In both cases, the structure of the distal end of the B ultrasound probe is unclear, and MRI technology is not affected by the gas in the intestine and the pelvic bone.

Domestic MRI technology is less applied in obstetrics, and it has been widely used abroad, but it is still used as an auxiliary technology for B-ultrasound technology.

3. After childbirth or induction

Perform a detailed examination of the placenta, membranes, umbilical cord, and fetus after induction or delivery. Fetal survival can be performed by various imaging or interventional endoscopy according to the situation, such as autopsy and histological examination if the fetus is dead.

4. Chromosome inspection

As far as possible, the fetus should be examined for chromosomes.

Amniotic band syndrome diagnosis

Clinical characteristics

Amniotic band syndrome has the characteristics of low incidence and sporadic disease, and has no clinical characteristics. There are no clinical symptoms and signs in the first trimester. If there is no obvious oligohydramnios in the first and second trimesters, the rate of uterine growth is normal.

2. Imaging examination

Including B-ultrasound and MRI. On the basis of imaging data, the diagnosis of amniotic band syndrome must meet the following factors: no history of viral or protozoal infection during pregnancy, no history of intrauterine surgery, no history of medication, normal fetal chromosomes, and no apparent hereditary fetus Deformity history.

Differential diagnosis of amniotic band syndrome

Amniotic membrane

It consists of two layers of amniotic membrane and two layers of chorion, with free edges and thick base, and sometimes blood flow is seen, which is thicker than the amniotic band. Causes: intrauterine instrument operation injury; uterine cavity adhesion, chorion growth along the intrauterine scar. The amniotic membrane is not attached to the fetal body, does not cause deformities, and can disappear in the third trimester. Amniotic membranes are mainly distinguished from the amniotic bands. Others that need to be distinguished from the amniotic bands are the incomplete mediastinal uterus and the amniotic diaphragm between the two amniotic cavities of twin pregnancy.

2. Extraembryonic body cavity

During the normal development of the embryo, the amniotic membrane and chorion are not completely fused, and the amniotic membrane and subchorium effusion, forming an extraembryonic body cavity. The characteristic is that the amniotic sac is intact, does not attach to the fetal body, the fetal movement is not restricted, and it does not incorporate fetal malformations. The extraembryonic body cavity usually disappears at 16 weeks of gestation.

3. Short umbilical syndrome

It is also known as lower abdomen exposed with incomplete deformities of the lower limbs and complicated deformities of the abdominal wall. At 4 to 6 weeks of embryo development, due to blood flow changes, embryonic tissues are underdeveloped or defective, causing internal bleeding, necrosis, hypoxia, and failure to close the abdominal wall. The performance is similar to that of amniotic band syndrome. Short umbilical syndrome has obvious short or no umbilical cord, obvious scoliosis, abdominal cavity reaching extraembryonic body cavity, combined with multiple deformities of spine limbs. In addition, no amniotic band echo was seen in the lower uterine cavity of the B-ultrasound.

4. Extra-amniotic pregnancy

The cause is similar to the external cause of amniotic band syndrome, the amniotic membrane ruptures, and the fetus grows into the extraembryonic body cavity. The rupture time of amniotic membrane is relatively late, the adhesion between amniotic membrane and villi is lost, and it will not adhere to the fetus, so generally there will be no fetal malformation.

Amniotic band syndrome treatment

1. Let it go and recover on its own after childbirth. It is mainly aimed at mild deformities and has little effect on the fetus and newborn.

2. Not treated during pregnancy, and then treated after full-term delivery.

3. Induction of labor is mainly aimed at the dead fetus, serious or important organ deformity, which has a long-term and short-term impact on fetal growth and development. Family members require termination of pregnancy, and the neonatal or fetal medical level is poor.

4. Intrauterine treatment (intrauterine surgery): Fetal surgery is a new discipline developed in recent years. At present, intrauterine treatment of various fetal malformations or structural abnormalities has been successfully performed. The most common procedure for amniotic band syndrome is amniolysis. After intrauterine surgery of the fetus with amniotic band syndrome, some abnormalities are reversible. For example, after the adhesion of the limbs is removed, the narrowed areas resume normal growth and development.