Velocity of head growth during the perinatal period.

Growth velocity of head circumference was studied longitudinally in different gestational age groups of 222 appropriate-weight-for-dates (AFD) and 94 small-for-dates (SFD) healthy infants during the first 5 months of life. Term AFD and SFD infants showed a steady slowing of growth rate of head circumference from birth. In contrast, preterm AFD infants of less than 36 weeks' gestation showed an increasing velocity of growth followed by slowing, with maximum velocity occurring between 30 and 40 days after birth. The shorter the postconceptional age at birth the later maximum velocity occurred. However, those preterm AFD infants of between 30 and 33 weeks' gestation who were given a high caloric feed showed a similar velocity curve to that of infants of 34-37 weeks of gestation. Cross-sectional data were used to estimate growth velocity of head circumference in the fetus. Two conclusions emerged. First, there is a slowing of head growth velocity from 31 weeks' gestation in utero, and second, term infants show a marked increase in volocity after birth. Though the occurrence of maximum velocity of head growth is delayed in the preterm infant, the net effect is such that at a given postconceptional age his head circumference is greater than that of the term infant, at least within the first 5 postnatal months.