INTRODUCTION:

Definition: Amniotic Band Syndrome (ABS) is a group of congenital abnormalities caused by bands of amnion (inner lining of the “bag of waters”) that attach to the fetus. It is caused by entrapment of fetal parts (usually limb or digits) in fibrous amniotic bands while in utero. The congenital malformations are ranging from minor constriction rings and lymphedema of the digits to complex, bizarre multiple congenital anomalies. The timing of the rupture is believed to occur between 28 days after conception to 18 weeks of gestation. However, late bands can occur and present at birth with multiple abnormalities of the limbs, even after a normal sonogram was performed earlier in gestation.

Synonyms /Alternative Or Additional Names Of Amniotic Band Syndrome (ABS): Amniotic Band Syndrome (ABS) has other terminologies or names. They are; Amniotic Deformity, Adhesions and Mutilations, Amniotic band disruption complex or sequence, Amniotic bands and sheets, Annular constriction bands, Congenital ring constriction, Constriction Band Syndrome and Amniotic Constriction Band Syndrome, Intrauterine amputation, Streeter's dysplasia, TEARS (The Early Amnion Rupture Spectrum), Congenital Transverse Defects or Deficiency, Limb-body Wall Complex, Amniotic deformity adhesions mutilations (ADAM), ADAM Complex, Amniotic band sequence, Amniochorionic mesoblastic fibrous strings, Congenital amputation, Congenital constricting bands and Tissue bands .

Types of ABS: Amniotic Band Syndrome (ABS) is classified in to two types. They are;

a. A membrane formed at an early stage of Pregnancy

b. A membrane formed at late stage of Pregnancy

a. A membrane formed at an early stage of Pregnancy: This type may cause severe damage to the structure of the various tissues, resulting in deformities in a large number of organs – this often results in intrauterine death. Defects in these cases usually include defects in the location and structure of the heart, omphalocele, gastroschisis, anencephalus, cleft face, hydrocephalus, etc.

b. A membrane formed at late stage of Pregnancy: This type may not cause damage, but if it does, this is usually to limbs. The entire limb, part of it, or only digits can be involved, and the result can be limb stumps or scars in one or more limbs. Often those fingers that are not missing in the limb involved have signs of scarring or fusion.

Epidemiology: Amniotic Band Syndrome (ABS) is an uncommon fetal malformation with increasing prevalence. It affects approximately 1 in 1,200 to 1 in 15,000 live births and to be the cause of about 178 in 10,000 miscarriages. About 80% of cases involve the hands and fingers and a significant number of clubfoot cases are correlated with ABS. It affects males and females in the same proportion.

Prenatal Risk Factors: The associated prenatal risk factors of Amniotic Band Syndrome (ABS) are

a. No distinct sex predilection has been determined.

b. Nearly sixty percent of the cases have some sort of abnormal gestation history.

c. Prenatal risk factors associated with amniotic band syndrome include prematurity (<37 weeks), low birth weight (<2500 g), maternal illness (during pregnancy), maternal drug exposure and maternal hemorrhage/trauma.

Causes of Amniotic Band Syndrome (ABS):

a. It is not the genetic or hereditary disease, so the likelihood of it occurring in another pregnancy is remote.

b. The amniotic band theory: the ABS occurs due to a partial rupture of the amniotic sac. This rupture involves only the amnion, the Chorion remains intact. Fibrous bands of the ruptured amnion float in the amniotic fluid and can encircle and trap some part of the fetus. As the fetus grows the bands do not, it become constricting. The constriction reduces the blood circulation and causes the congenital abnormalities. In some cases, a complete “natural” amputation of a digit(s) or limb may occur before birth or necrosis occur which require surgical amputation after birth.

c. The vascular disruption theory: it is due to “intrinsic” defect of the blood circulation.

d. Families with connective tissue disorders.

e. The Minority causes are Maternal trauma, Oopherectomy during pregnancy, Intrauterine contraceptive device, Amniocentesis and Monozygotic twinning (works as teratogenic stimulus)

f. Ehlers-Danlos Syndrome and Osteogenesis Imperfecta

Pathogenesis Amniotic Band Syndrome (ABS):

Symptoms of Amniotic Band Syndrome (ABS):

Constriction rings around the digits, arms and legs, Swelling of the extremities distal to the point of the constriction, Amputation of digits, arms and legs, Asymmetrical facial, Cephalocele, Anencephaly, Multiple joint contractures, Pterygium, Club hands and pseudosyndactyly, Microphthalmia, Uveal coloboma, corneal metaplasia, Unilateral chorioretinal lacunae, Clubbed feet, Missing limbs, Simion crease, Skull defect, Visceral defect, Structural deformities, Limb abnormalities, Spine defect, Lung abnormalities, Facial abnormalities, Skull abnormalities, Abdominal abnormalities, Chest abnormalities, Reduced amniotic fluid, Leakage of amniotic fluid, Absence of kidneys, Bilateral cystic kidneys and Obstruction to urine outflow from kidneys

Diagnosis: It is very difficult to detect before birth. But even then it can be found by Ultrasound scan, 3D Ultrasound scan and MRI, and Fetal Karyotype

Differential Diagnosis: a. Amniotic folds, b. Short umbilical cord syndrome or limb-body wall complex or body stock anomaly, c. Extra amniotic pregnancy

a. Amniotic folds- are recognised by prenatal ultrasonography as reflecting membranes floating freely in the amniotic fluid.

b. Short umbilical cord syndrome or limb-body wall complex or body stock anomaly- this is complex set of disruptive abnormalities having in common the failure of closure of the ventral body wall.

c. Extra amniotic pregnancy- Rupture of the amnion is occurring later when the amnion and Chorion have lost their “stickiness”.

Features or Stages of Amniotic Band Syndrome (ABS):

The constriction of appendages by amniotic bands may result in:

• Restrictions of the growth around the digits, arms and legs

• Constriction rings around the digits, arms and legs - the bands will partially constrict the blood flow in the affected appendage causing a deep groove in the baby's skin

• Swelling of the extremities distal to the point of constriction (congenital lymphedema)

• Amputation of digits, arms and legs (congenital amputation)

Other Bands:

• Other less common types of band-like appearing structures may also be observed on obstetric sonogram.

• These include: chorio-amniotic separation (normal finding in the 1st trimester up to 16 weeks), velamentous cord insertion, uterine fusion abnormalities (bicornuate, septate uterus, etc.), and remaining membranes after demise of a twin.

• In these situations, correlation of ultrasound features with patient's clinical history can be useful.

Approach In Evaluating Band-Like Structures

The following diagram can be utilized to aid diagnosis when a band-like structure is visualized in the uterus.

Prevention:

• Amniotic band syndrome is considered an accidental event and it does not appear to be genetic or hereditary, so the likelihood of it occurring in another pregnancy is remote.

• The cause of amnion tearing is unknown and as such there are no known preventative measures.

Interventions and Treatment:

Treatment usually occurs after birth and where plastic and reconstructive surgery is considered to treat the resulting deformity. Plastic surgery ranges from simple to complex depending on the extent of the deformity. Physical and occupational therapy may be needed long term. In rare cases, if diagnosed in utero, fetal surgery may be considered to save a limb which is in danger of amputation or other deformity. This typically would not be attempted if neither vital organs nor the umbilical cord are affected.

A. Fetal Treatment:

• In utero limb salvage: fetoscopic release of amniotic bands for threatened limb amputation.

• Fetoscopic laser release of amniotic bands in extremity ABS offers the potential to prevent limb amputation

• A small camera is inserted through the mother’s abdomen and uterus into the amniotic sac in order to see and cut the bands.

• Cutting the amniotic bands is performed utilizing a fetoscopic technique.

• The procedure is typically performed under regional anesthesia.

• Early fetoscopic release may prevent amputation and allow improved limb development.

B. Child Treatment:

• Indications for intervention depend on the medical stability of the child and on the neurovascular status of the limb.

• Bands that only cosmetically affect the superficial skin generally do not require any intervention.

• Only the tight constriction bands, resulting in gross lymphedema, vascular compromise, or both necessitate immediate surgical release.

• Surgery also is indicated for patients with syndactyly or acrosyndactyly that compromises hand function. Thumb amputation (which is rare), club feet, cleft lip, and cleft palate require reconstruction, but these procedures can be performed electively at a later time.

Special Considerations for Delivery:

• Type of delivery - Typically, pregnancies with ABS do not require cesarean delivery. The need for fetal intervention should not impact the mode of delivery. The delivery plan can carefully discussed.

• Place of delivery - If all the prenatal monitoring suggests that the baby is doing well, the baby can be delivered at the hospital. However, the hospital should be prepared to handle any immediate needs of the newborn and have a neonatal intensive care unit with the capability to provide specialized care.

• Time of delivery - Unless there are signs of serious complications of ABS, there is no reason to intentionally induce an early delivery. The team at the Center may recommend early delivery for pregnancies that appear to be in danger

Follow-Up:

Ø All patients with ABS should be monitored regularly until skeletal maturity is reached, because of the potential for recurrence of the rings and for secondary contractures that may develop

Ø The prognosis is good for limbs affected by isolated superficial extremity bands. Aside from cosmetic irregularities, no functional defects are usually present. Deeper bands may be associated with progressive problems leading to lymphatic and neurovascular compromise that requires operative intervention.

Ø For patients with acrosyndactyly, hand function is limited secondary to stiffness of the joints, but reconstruction can result in good prehension and grasp. Children whose limbs have been amputated in utero usually adapt well to their physical limitations, and aside from fitting with prosthesis, little often needs to be done. In children with a transverse deficiency proximal to the ankle joint, prosthesis is required for full function.

Prognosis:

v The prognosis depends on the location and severity of the constricting bands.

v Every case is different and multiple bands may be entangled around the fetus.

v Bands which wrap around fingers and toes can result in syndactyly or amputations of the digits.

v In other instances, bands can wrap around limbs causing restriction of movement resulting in clubbed feet.

v In more severe cases, the bands can constrict the limb causing decreased blood supply and amputation.

v Amniotic bands can also sometimes attach to the face or neck causing deformities such as cleft lip and palate.

v If the bands become wrapped around the head or umbilical cord it can be life threatening for the fetus.

CONCLUSION:

Amniotic Band Syndrome (ABS) is very difficult to diagnose and even ultrasound doesn’t reveal it. Although the incidence is very low, the pregnant woman with decreased fetal heart rate and history of amniocentesis must be monitored vigilantly and at viable gestational age, immediate delivery may be indicated.

REFERENCES:

1. Diana B et al. Fetology Diagnosis and Management of Fetal Patient. McGraw-Hill, New York. 2^nd ed. 2010.

2. Cunningham et al. Williams Obstetrics. McGraw-Hill, New York. 23^rd ed. 2010.

3. Peter WC. Ultrasonography in Obstetrics and Gynecology. Saunders Elsevier. 5^th ed. 2008.

4. John et al. Manual of Neonatal Care. Lippincott. 6^th ed. 2008.

5. Ross MG. Pathogenesis of Amniotic Band Syndrome. American Journal of Obstetrics and Gynecology. 197(2); 2007: 219-20.

6. Cincore V, Ninios AP, Pavlik J, Hsu C. Prenatal Diagnosis of Acrania associated with Amniotic Band Syndrome. Obstetrics and Gynecology. 102(5); 2003: 1176-8.

7. www.fetalcarecentre.org

8. www.amnioticbandsyndrome.com

Received on 25.06.2011 Modified on 20.08.2011

Asian J. Nur. Edu. & Research 1(2): April-June 2011; Page 41-44