Non-nutritive sucking in the healthy pre-term infant.

In the infant, sucking behaviour is one of the first coordinated muscular activities. It is under the control of the brainstem. In utero sucking is observed from 13 weeks' gestation. The healthy full-term newborn infant has a very stable rhythm of alternating bursts of sucking with pauses in between. The non-nutritive sucking (NNS) patterns of 58 low-risk prematurely born infants (gestational ages between 26 and 35 weeks) were studied using a specially designed computer-based method that analyses and quantifies NNS. A total of 183 observations were analysed. The typical NNS pattern with bursts of sucking activity separated by quiescent periods was recorded in all infants studied and was already present before 30 weeks of gestation. A gradual change over time of their NNS was seen. With increased maturation the sucking activity, sucking frequency, amplitude and burst duration all increased, while the variability of the sucking frequency and the duration of the intervals between bursts declined. Post-menstrual age (PMA) was the dominant predictor of this result but gender, state of activity and weight also influenced it to some extent. Girls had more sucking activity and a higher sucking frequency than boys. State of activity affected the stability of the rhythm. The weight of the infant influenced both sucking activity and duration of separate bursts.