Effects of atypical patterns of fetal growth on newborn (NBAS) behavior.

Newborn infants who showed anthropometric signs of atypical patterns of fetal growth were compared with infants of appropriate growth on the Neonatal Behavioral Assessment Scale (NBAS) and on recently developed supplementary items. The sample consisted of lower-socioeconomic-status families in San Juan, Puerto Rico, and included teenage and older mothers. Infants with atypical patterns of fetal growth showed lower scores than did infants of appropriate growth on the NBAS orientation, motor, and reflex clusters and on 15 of the 18 supplementary scores. Gestational age was covaried and showed independent effects on 6 items. Differential effects on measures of state and autonomic function were also found when the effects of the ponderal index were held constant. The results suggested that neonatal behavior is related to multiple indices of fetal growth patterns that may indicate early versus late nutritional insult. Supplementary NBAS items do not improve the discriminability of the NBAS but may help explain the basis for observed group differences.