Amniotic band syndrome

Pathology description

The fetus develops in the cavity of the uterus, which is covered by a thin double membrane called the amnion, which is normally well attached to the inner wall of the uterus and placenta. In rare circumstances, a part of this membrane, or band, disengages and may be left floating in the uterine cavity.

When this occurs, fetal body parts can become entangled in an amniotic band, which can constrict them. Of all the parts of the fetal body, the limbs (arms, legs, hands, feet, and fingers) are the most at risk of becoming entangled in an amniotic band. If the tangle is tight enough to reduce blood flow in the limb, the development of the limb may be affected. When an amniotic band causes such damage to a part of the fetal body, it is called amniotic band syndrome.  

Amniotic band syndrome is very infrequent, affecting fewer than 1 in 5000 newborns. It is usually diagnosed at birth, but can sometimes be detected in utero by ultrasound.  

Why does it occur?

The cause is unknown, but it rarely has a familial or genetic origin, and it may also result from amniocentesis or fetal surgery. 

Amniotic band syndrome can occur when the amniotic membrane is damaged during pregnancy and the amnion disengaged. When this happens, thin strands of tissue (amniotic bands) form within the amniotic cavity. These bands are very adhesive and can become entangled around the developing fetus, restricting blood flow and thus affecting the growth of certain parts of the body.  

What consequences can amniotic band syndrome have for fetal development?

The type of problems that amniotic bands produce depends on when the body part is trapped during pregnancy,whether or not the blood flow is cut off, and of course whether other areas of the body are trapped or attached. 

It is usually a limb that becomes entangled in an amniotic band. The distal parts of the limb (hands, feet and fingers) are at risk of various problems. When the limb is compromised, there may be swelling of the distal parts, developmental abnormalities with physical deformity or even a complete amputation. 

Less frequently, an amniotic band can also affect the development of other parts of the body and produce large, sometimes irreversible and deformed lesions, such as if the band passes over the trunk, face, penetrates the brain or affects the genitals.

There are also cases in which the amniotic band surrounds the umbilical cord of the fetus, causing obstruction of blood flow and fetal death.  

Diagnosis

The diagnosis of mild cases is usually made after birth while prenatal diagnosis is usually made in the most serious cases, when sometimes we can already see irreparable injuries by ultrasound. But in some cases fetal surgery can improve the postnatal prognosis of associated lesions, or can even save fetal life if the umbilical cord is being compressed by a band. 

Treatment

The goal of fetal surgery is to release the constriction caused by the amniotic band before it can cause more damage.

Fetal surgery is performed by fetoscopy in the operating theatre. Under local anaesthesia, a minimal incision of about 3 mm is made in the abdomen of the pregnant woman and with ultrasound control the endoscope is inserted into the uterine cavity. In this way, the direct visualization of the amniotic bands and the degree of involvement of the different fetal parts is enabled and the possibility of achieving their release through various surgical techniques is evaluated.

The success of fetal surgery depends on the degree of damage caused by the amniotic band. If the distal part of the limb is swollen, the release of the band allows the swelling to resolve and normal development to continue. If the constriction has been more severe, the release of the band can stop further damage and even prevent distal amputation of the affected limb. 

What appointments are needed for fetal surgery?

An in-patient admission of the pregnant woman will initially last 1–2 days and afterwards weekly check-ups with examination and ultrasound will be required, and she will have to maintain a low-activity lifestyle mainly at home until the end of pregnancy, especially for the first 3-4 weeks after the intervention. Normally, childbirth can be performed at term without any need to induce it prematurely. 

Treatment after birth consists of plastic and reconstructive surgery, followed by physiotherapy and occupational therapy, as required by the type of involvement.  

During pregnancy, you will receive the support of nurses specialized in fetal medicine, not only on a technical level but also on an emotional level throughout the process. In addition, we can put you in contact with other families who have gone through the same experience. This is very positive and helps to humanize and understand the problem in a much more intuitive way and without the difficulties that sometimes arise when receiving only technical information from professionals.