Posterior homeotic transformation of the cervical-thoracic border is a marker of maldevelopment in humans

This study was initiated after observing a high incidence of cervical ribs in stillborn fetuses referred for autopsy at our institution. The study establishes the prevalence of cervical ribs in this referral population and describes related associations. Radiologic data were reviewed from 389 stillborn and 171 liveborn autopsies performed at Primary Children's Medical Center from 2006 to 2011. Cervical ribs were identified in 49.1% of stillborn fetuses and 22.8% of liveborn infants at the time of autopsy. There was a statistically significant high association of cervical ribs in patients with aneuploidy. Karyotypes were available on 186 of the stillborn cases (47%). Of the patients with chromosome abnormality, 24 of 32 (75%) had cervical ribs. Our findings support the hypothesis that cervical ribs, a posterior homeotic transformation of the cervical-thoracic border, represent disadvantageous development during early stages of blastogenesis. This same region and patterning of the anterior to posterior skeletal axis has been conserved throughout evolution in almost all mammals.