• Amniotic Band Syndrome / ABS Overview

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    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. Abnormalities result from attachment or constriction that lead to:

    • Webbing of fingers and / or toes
    • Amputation of limbs
    • Severe defects of the head and face, spine, umbilical cord and / or body wall

    There are several theories as to the cause of Amniotic Band Syndrome / ABS. The most widely accepted is a rupture of the amnion occurring early in gestation. The fibrous bands of amnion that occur from the amniotic rupture encircle the limbs, resulting in tourniquet-like defects and intrauterine amputations. 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.

    Amniotic band syndrome is difficult to diagnose. Estimates of amniotic band syndrome / ABS incidence vary widely, from one in 1,200 to one in 15,000 live births.

    The earliest amniotic bands have been detected was at 12 weeks gestation, by vaginal ultrasound. Bands may be difficult to detect by ultrasound, and are more often diagnosed by the effect they have on fetal anatomy, as in the case of missing or misshapen limbs.

    If amniotic band syndrome is suspected, a detailed ultrasound should be conducted to assess any and all abnormalities. A fetal echocardiogram will identify associated cardiac defects. A fetus with amniotic band syndrome should pose no increased risk for the mother during pregnancy. The diagnosis of amniotic band syndrome, however, identifies a pregnancy as being at increased risk for fetal anomalies and premature labor and delivery.

    The vast majority of cases of amniotic band syndrome / ABS are best managed after the baby is born. In rare instances, fetal intervention may be possible to cut amniotic bands which may threaten to amputate a limb or constrict the umbilical cord.