Does gestational duration within the normal range predict infant neuromotor development?

To examine the extent to which infant neuromotor development is determined by gestational duration and birth weight within the normal range.

The study was embedded within the Generation R Study, a population-based cohort in Rotterdam, the Netherlands. An adapted version of Touwen's Neurodevelopmental Examination was used to assess 3224 infants (1576 males and 1648 females) at corrected ages between 9 and 15 weeks. Non-optimal neuromotor development was defined as a score in the highest tertile.

Infant neuromotor development was significantly affected by gestational duration (odds ratio 0.8, 95% confidence interval 0.7;0.8). Adding a quadratic term of gestational duration to the model revealed a highly significant curvilinear association between gestational duration and neuromotor development; after adjusting for post-conceptional age this was still significant. Although babies with a 1 kg lower birth weight had a 30% higher risk of non-optimal neuromotor development, this association disappeared after adjustment for post-conceptional age.

Our findings indicate that differences in infant neuromotor development can be explained even by variations in gestational duration within the normal range. If an infant is found to have minor neuromotor delays, account should be taken of this.