The role of birthweight discordance in the intellectual and motor outcome for triplets at early school age.

Aim: We assessed motor and intellectual outcome in triplets at school age and investigated the predictive value of perinatal and demographic factors.

Methods: Seventy-one live-born newborn infants (24 triplet pregnancies) were prospectively enrolled at birth. At the age of 6 years, 58 children (31 males, 27 females; mean gestational age 31.2 wks [SD 2.2 wks]; mean birthweight 1622 g [SD 440 g]) returned for a neurodevelopmental examination. A comparison group for triplets born before 32 gestational weeks comprising 26 gestational age-, birthweight-, and sex-matched singletons was also recruited (mean gestational age 30.1 wk [SD 1.5 wk]; mean birthweight 1142 g [SD 210 g]; 12 males, 14 females). The Zurich Neuromotor Assessment was used to examine motor performance, and intellectual abilities were assessed with the Kaufman Assessment Battery for Children (K-ABC).

Results: Motor performance and movement quality in these individuals was significantly reduced compared with the test norms for all motor tasks (p<0.001) other than static balance. The mean values on the Mental Processing Composite (95.3, SD 8.4) and the Achievement Scale (90.1, SD 13.8) of the K-ABC were also lower than those in the test reference (p<0.05 and p<0.01 respectively). Triplets born at less than 32 weeks' gestation showed poorer pure motor and adaptive gross motor performance (both p<0.05) than, but similar intellectual performance to, the gestational age-, birthweight- and sex-matched singletons. Poor outcome was predicted by low socio-economic status and by intertriplet birthweight discordance (both p<0.01).

Interpretation: Triplets were at an increased risk of mild motor and intellectual impairments. This finding is important for tailoring therapeutic interventions for these children and for parental counselling. Very preterm triplets showed similar outcomes to the singleton comparison children, except that they had poorer motor performance. Low socio-economic status was a major risk factor for impaired intellectual development. In addition, birthweight discordance may also be considered a predictor for poor long-term motor and intellectual outcome in triplets.