Amniotic band syndrome, also known as constriction ring syndrome, occurs when the placenta of a developing baby is damaged while the infant is still in the womb. This damage can cause strands of amniotic fluid to break free from the placenta and constrict the growth of the baby's face, arms, legs, fingers or toes. The strands wrap around the fetus, causing an effect similar to when you wrap a rubber band around your finger.
Because of the random nature of amniotic band syndrome, the deformities that it cause vary. Some infants with the syndrome are born with an abnormal gap in the face, amputation of an arm, leg, finger or toe, or deformity to the abdomen or chest.
Amniotic band syndrome is usually diagnosed at birth, but in some cases may be diagnosed before birth via ultrasound. In most cases, the defect it causes is not severe and the child will just have a small indentation or cleft in the affected area. In these minor cases, treatment is not necessary. The syndrome is usually cosmetic and does not affect function of the affected area. If more severe damage or amputation occurs, doctors may be able to reconstruct part of a missing limb. If surgery is necessary, it is usually performed after the child turns one.
Amniotic band syndrome is rare, occurring in just 1 in 10,000 to 15,000 live births. In most cases, the syndrome is random, occurring for no apparent reason. The syndrome does not carry increased risks for the pregnant mother. However, in some rare cases, the syndrome can cause miscarriage if the band wraps around the umbilical cord, restricting the fetus's nutrition.