Metopic craniostenosis as a consequence of fetal head constraint: two interesting experiments of nature.

Two instances of metopic craniosynostosis provide dramatic experiments of nature which implicate fetal head constraint as one cause of early sutural fusion. The presumed restriction of growth stretch at the metopic suture in one instance was due to a bicornuate uterus in which the fetal head was markedly constrained. The second instance was in one of monozygotic triplets reared in a small mother in which the affected fetal head had been wedged between the hips of the two unaffected siblings.