Assessment of gestational age by neurological examination

Abstract

A number of reflexes has been studied in 219 standard neurological examinations carried out on 62 infants born at known gestational ages between 25 and 42 weeks. 37 of the infants were of normal birthweight for their gestational age, and 25 were small-for-dates (defined as more than 25% below the mean birthweight for their gestational age). The palmar and plantar grasp, the abduction phase of the Moro reflex, and the withdrawal reflex on stimulation of the sole of the foot were constantly present, and the Galant reflex and blink response to light were almost constantly present, whatever the baby's gestational age. Another group of reflexes was absent in the most immature babies, appearing at predictable times in the latter third of the gestational period. The pupil reactions to light were present from 29-31 weeks' gestation, the glabellar tap reflex from 32-34 weeks, the traction response from 33-36 weeks, the neckrighting reflex from 34-37 weeks, and the response of head-turning to diffuse light from 32-36 weeks. The gestational age after which one of these reflexes is detectable is the same whether the baby has been maturing inside or outside the uterus. The gestational age at which a reflex appeared was also the same in snall-for-dates babies as in those having a normal birthweight for their gestational age. The presence or absence of these reflexes can therefore be used to assess the gestational age of a baby of low birthweight and to determine whether it is small-fordates or truly premature. The presence of certain other reflexes, such as the crossed extensor reflex and the adduction phase of the Moro reflex, also depended on gestational age, but the relationship was too inconstant for them to be reliable indices of gestational age. The method is compared with other work on neurological maturation in premature infants, and the theoretical and practical interest of the results is discussed.