Research Overview - A Whole of Population Study of Term and Post-Term Gestational Age at Birth and Children’s Development

The objective of this study was to examine the patterns of risk of poor child development among 12,601 Australian children born at term and post-term. The Australian Early Development Index (AEDI) was used to collect data on child development. This is a holistic measure of children’s development at school entry (median age 5 years) that demonstrates predictive validity for later school achievement. This measure assesses five developmental domains: physical health and wellbeing, language and cognitive skills, emotional maturity, social competence, and communication and general knowledge. The AEDI was completed by teachers during a 2009 national census of children attending their first year of school. 

The results of this particular study revealed that across all developmental domains, children born at 37–39 weeks’ gestation had a slightly higher risk of being developmentally vulnerable compared with children born at 40 weeks, with the risk tending to decrease as gestational age at birth approached 40 weeks. The lowest vulnerability was found among children born at 40– 41 weeks’ gestation. The researchers found minimal effects of gestational age on physical readiness for the school day and a slightly higher risk of vulnerability on the other two domains (physical independence and gross and fine motor skills) for children born post-term. In this study there were higher risks of developmental vulnerability among children born at early term and post-term gestational ages, compared with 40 weeks. These effects were perhaps most noticeable on the Language and Cognitive skills, Social Competence and Physical Health and Wellbeing domains.

Suggestions as to the likelihood by which early term or post-term gestational age at birth affect development of otherwise healthy children were provided. The last area to mature in the weeks prior to birth includes the grey matter volume, particularly in the parietal lobe. The authors speculated (though no supporting evidence to suggest so), how the parietal lobe contributes to auditory processing and language ability, and this may explain the higher risk of vulnerability on the Language and Cognitive skills domain compared with other domains. For children born post-term, the mechanisms for the increase in developmental vulnerability is thought to be related to placental changes such as poorer perfusion.

The results of this study demonstrate that developmental vulnerability of children born at 37 weeks or ≥42 weeks is not equivalent to being born at 40 weeks. This has important implications for induction prior to 40 weeks for non-medical or non-obstetric reasons. Overall, these results suggest that children born at 40 and 41 weeks’ gestation have the lowest risk of developmental vulnerability, and each additional week of gestation within the ‘term’ range (37–41 weeks) is important for children’s future development.
Smithers, L.G., Searle, A.K., Chittleborough, C.R., Sheil, W., Brinkman, S.A., & Lynch, J.W. (2014). A whole of population study of term and post term gestational age at birth and children’s development.  International Journal of Obstetrics and Gynaecology. 122(10), 1303-11. doi: 10.1111/1471-0528.13324.