Amniotic Band Syndrome

February 1, 2007

This full-term infant was born with malformed feet and toes. Physical examination findings were otherwise normal. The child weighed 3.1 kg (6.9 lb) at birth; her Apgar scores were 9 at 1 minute and 9 at 5 minutes. Her mother (21-year-old gravida 2 para 1) had an unremarkable antenatal history and a normal vaginal delivery. There was no family history of congenital anomalies.

This full-term infant was born with malformed feet and toes. Physical examination findings were otherwise normal. The child weighed 3.1 kg (6.9 lb) at birth; her Apgar scores were 9 at 1 minute and 9 at 5 minutes. Her mother (21-year-old gravida 2 para 1) had an unremarkable antenatal history and a normal vaginal delivery. There was no family history of congenital anomalies.

This infant's deformities were attributed to amniotic band syndrome (ABS), a group of congenital abnormalities, also known as Streeter dysplasia and amniotic band sequence, writes Bhagwan Das Bang, MD, of Opp, Ala. The estimated incidence varies from 1:1200 to 1:15,000 live births. The cause, although unclear, is related to rupture of the amnion between 28 days and 18 weeks of gestation and the release of fibrous bands that ensnare the fetus. Constriction bands around the head or umbilical cord can result in fetal death. More commonly, the bands wrap around the extremities and cause partial constriction of a limb or digits, such as mild elephantiasis or webbing. Severe constriction may result in amputation.

Amniotic bands have been detected by vaginal ultrasonography as early as 12 weeks.1 The bands themselves may be difficult to detect with this method. However, their effect on the fetal anatomy (ie, missing or misshapen limbs) is usually evident on an ultrasonogram unless the effect is mild--such as the digital anomalies seen in this infant.

Craniofacial defects associated with ABS include cleft lip and palate, anophthalmia or asymmetric microphthalmos, anencephaly, and encephalocele. In patients who have anencephaly associated with ABS, a portion of the calvaria remains, usually near the base or orbit, unlike classic anencephaly, in which the bones are symmetrically absent. Encephalocele in ABS typically develops asymmetrically outside the midline. Abnormalities of the viscera may include omphalocele and gastroschisis. Abdominal wall defects are typically large and can be associated with severe spinal deformities.

Most cases of ABS are sporadic; there is no risk of recurrence in subsequent pregnancies.1 However, ABS has been linked to underlying disorders, such as Ehlers-Danlos syndrome type III and osteogenesis imperfecta. There have also been reports of ABS occurring with exposure to teratogens (eg, methadone and lysergic acid diethylamide).

This infant will be periodically evaluated by a pediatric orthopedic surgeon in case surgical correction of the malformed feet and toes is required for cosmetic reasons or because of impeded ambulation.

References:

REFERENCE:


1. Amniotic Band Syndrome/ABS. Fetal Care Center of Cincinnati Web site. Available at:

http://www.fetalcarecenter.org/medicine/therapies/abs/abs-details.htm

. Accessed January 10, 2007.