Temperament prediction for neonate twins: relation to size for gestational age in same-sex pairs

Infants from 22 pairs of appropriate-for-gestational-age/small-for-gestational-age (AGA/SGA) same-sex twins were assessed for temperament stability between the neonatal period and 30 months of age. The evaluation of neonatal temperament included observers' ratings of irritability, resistance to soothing, activity level while awake, activity level during sleep, reactivity, and reinforcement value. At 6, 9, 12, 18, 24, and 30 months mothers rated their infants' temperament on standardized questionnaires which yielded nine temperament categories: activity level, rhythmicity, approach or withdrawal, adaptability, intensity of reaction, quality of mood, attention span, distractibility, and threshold of responsiveness. The Bayley Scales of Infant Development were administered at 6, 9, 12, 18, 24, and 30 months to assess mental development. The results of longitudinal correlational analyses indicated that, for the AGA infants, there was a pattern of significant predictive relations between the neonatal ratings of temperament and maternal ratings of temperament at 6, 9, 12, 18, 24, and 30 months. The SGA infants did not demonstrate similar behavioral stability from the lying-in period up to 30 months of age. Furthermore, for AGA infants there was a consistent trend for both reactivity and neonatal activity during sleep to predict mental development scores between 6 and 30 months. A similar pattern was not observed for the SGA cotwins. The results indicated that temperament stability is an additional area of risk for SGA twins, and that the developmental function of the underlying processes in the neonatal measures is different for AGA and SGA infants.