Monozygotic twinning, cerebral palsy and congenital anomalies.

BACKGROUND The majority of cases of cerebral palsy (CP) have their pathogenesis during fetal development and are a form of congenital anomaly, the aetiology of which is uncertain. Anomalous development of other organs evident at birth is also a congenital anomaly. A small proportion of these are known to be caused by chromosomal or gene abnormalities, environmental teratogens and dietary deficiencies. The majority are of unknown aetiology. METHODS A review of monochorionic (MC) monozygotic (MZ) placentation in the pathogenesis of congenital anomalies and CP was conducted using the PubMed, MEDLINE, EMBASE and Cochrane databases. RESULTS Zygote division and MC placentation have serious implications for the development of both conceptuses. Most reports observe predominantly cerebral abnormalities in one or both conceptuses. These cerebral abnormalities often present as CP or other disabilities attributable to central nervous system impairment. In addition to the anomalies in central nervous system development, anomalies in the fetal development of a wide variety of other organs have been reported with MC MZ twinning. CONCLUSIONS CP and congenital anomalies share a common pathogenic mechanism attributable to MZ twinning. These abnormalities in singletons are coincident with very early loss of one conceptus. The quantitative contribution of monozygosity and monochorionicity to the genesis of CP and congenital anomalies needs to be made.