Triplets across the first 5 years: the discordant infant at birth remains at developmental risk

To examine whether the risk posed to infant development by triplet birth persists into childhood and whether growth-discordant triplets are at a particularly high developmental risk.

Twenty-one sets of triplets were matched with 21 sets of twins and 21 singletons (N = 126) for medical and demographic conditions and were followed from birth to 5 years. At 6, 12, and 24 months, cognitive development was assessed and mother-infant interactions were coded for maternal sensitivity and child social engagement. At 5 years, the children's cognitive development and neuropsychological skills were tested, social engagement was coded from mother-child interactions, and behavior problems were examined. Maternal adjustment was assessed during interviews at 1 and 5 years.

Although triplets showed lower cognitive performance at 6, 12, and 24 months as compared with singletons and twins, differences were attenuated by 5 years in both global IQ and executive functions. Similarly, the lower social engagement observed across infancy and the higher internalizing symptoms reported at 2 years for those in the triplet group were no longer found at 5 years. Difficulties in maternal adjustment among mothers of triplets decreased from 1 to 5 years. However, in 65.2% of the initial sample there was a weight discordance of >15% at birth, and the discordant triplets showed poorer cognitive and social development as compared with their siblings across infancy. At 5 years, the discordant children demonstrated lower cognitive and executive functions performance, decreased social engagement, and higher internalizing symptoms as compared with both siblings and peers.

Whereas most triplets catch up after an early developmental delay, the risk for discordant triplets seems to persist into childhood. Such infants, who are at both biological and environmental risk, should receive special and consistent professional care.