Within-pair differences in newborn twins: Effects of gender and gestational age on behavior

Abstract

The behavior of 120 full term and 160 preterm newborn twins was assessed in several key areas: Irritability, soothability, reactivity, reinforcement value, and activity level. Infants were assessed during various situations so that aggregate, or summary, scores representing each behavioral area could be obtained. Evaluations were made during a feeding period, an active sleep period, an awake alert period during which orienting and interactional behaviors were observed, a quiet period during which reactivity to stress was observed, and any fussy periods during which irritability and soothability were assessed. Significant within-twin-pair concordance of behavior was obtained for each of the areas of behavior, suggesting the influence of constitutional variables on neonatal behavior. Analysis of these data by sex resulted in significant within-pair concordance of behavior for same-sex but not for opposite-sex twins. The actual ratings on these behaviors differentiated between full term and preterm infants. Increased behavior deviance was observed with increasing prematurity in the areas of soothability and activity level. The results are discussed in terms of increased risk factors for preterm twins.