The findings in fifty-nine patients with congenital constriction band
syndrome and in experiments in which limb malformations resembling those of
the human constriction band syndrome were successfully reproduced in rat
fetuses by amniocentesis indicated that these malformations arise from
excessive contraction of the uterine muscle during pregnancy, with
resulting hemorrhages from the marginal blood sinuses of the digital rays.
Such malformations in humans may arise during the fifth and sixth weeks
counted from ovulation. It therefore was concluded that this syndrome is
not hereditary but is produced by prenatal environmental factors.