Twinning on the brain: The effect on neurodevelopmental outcomes

Abstract

Twinning is currently considered a complex multifactorial trait. Few studies have explored how the unique genetic and environmental influences that create twinning affect phenotypes and outcomes. Previous data has shown that twins account for a significant proportion of preterm and low-birth-weight infants, who are at risk for longterm neurodevelopmental disabilities such as cerebral palsy and cognitive impairment. More recently, it has been postulated that even without these co-morbidities, twinning in and of itself may incur a neurodevelopmental disadvantage even among term newborns. The purpose of this review is to report primarily on neuromotor outcomes of twins compared to singletons. In addition, we describe specific environmental risk factors among twins which are associated with poorer outcomes. Several putative neurodevelopmental modulators are explored, including death of a co-twin, chorionicity, birth weight discordance, and twin-twin transfusion. By teasing out environmental influences that potentially influence neurocognitive outcomes, families can receive more specific counseling and developmental services can be provided to those twins at especially high risk. © 2009 Wiley-Liss, Inc.