Amniotic Band Syndrome (ABS)

Amniotic banding affects approximately 1 in 1,200 live births. It is also believed to be the cause of 178 in 10,000 miscarriages. ABS occurs due to a partial rupture of the amniotic sac. Fibrous bands of the ruptured amnion float in the amniotic fluid. and can encircle and trap some part of the fetus. Later, as the fetus grows but the bands do not, the bands become constricting. This constriction reduces blood circulation, hence causes congenital abnormalities. It is  often difficult to detect before birth. 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.

Full details are available on : http://en.wikipedia.org/wiki/Amniotic_band_syndrome