Gestational age within normal range and infants' health and temperament at 3-months of age.

OBJECTIVE: To examine the association between gestational age (GA) at birth across the normal GA spectrum (37-41 weeks) and the temperament and health of 3-month old infants.

METHODS: The sample comprised 242 "low-risk" mothers and infants without chronic illnesses or severe pregnancy complications. Infant temperament was defined by three constructs: Negative Affectivity (NA), Extraversion, and Regulation, assessed by parents' reports on the Infant Behavior Questionnaire. Infants' health was defined as the number of nonroutine doctors' visits attended by the infants since their release from the hospital after birth. Analyses employed a continuous measure of GA to assess outcomes across GAs and a categorical measure (37, 38, 39-41 weeks GA) to examine contrasts.

RESULTS: Extraversion was positively related to GA primarily due to the lower scores of infants born at 37 weeks compared to infants born at 39-41 weeks GA. NA showed a similar effect. The odds of infants born at 37 weeks attending a nonroutine medical visit were 2.8 times that of infants born full-term.

DISCUSSION: Infants born at 37 weeks GA express less affect and use more nonroutine medical services than do infants born at 39-41 weeks GA. The findings underscore the importance of considering the risks of pregnancy prolongation with the developmental risk associated with early-term delivery.