Parental communication and infant language development: the influence of premature birth and socioeconomic risk

Abstract

Preterm birth is birth occurring before 37 weeks gestation. Preterm birth is associated with an increased risk of impairment in many neurodevelopmental outcomes, including a higher risk of later language impairment and delay. Socioeconomic deprivation is also a known risk factor for later language difficulties. Moreover, mothers from a low socioeconomic background are at an increased likelihood of having a preterm birth. Socioeconomic deprivation is linked to a decreased rate of language exposure in early childhood, but it is unknown how prematurity influences this relationship. Longitudinal studies examining infant language output are required to untangle the contributions of both socioeconomic status and prematurity to poor language outcomes. The aims of this thesis were to investigate the relationships between gestational age at birth, socioeconomic deprivation, and language exposure, operationalised as parental gesture type and frequency during play in infancy. The creation of a novel coding scheme allowed for the capturing of parental language and gesture. I hypothesized that there would not be differences in the use of vocabulary and gesture of parents of preterm vs. term infants. I predicted that parents from a lower socioeconomic status would use less vocabulary and gesture when communicating with their infants. Finally, I explored relations between familial factors such as socioeconomic status, gestational age at birth, and parental communication at 9 months as predictors of infant language outcomes at 24 months.

47 parent-preterm infant dyads, mean gestational age of 29 weeks (range of 24-31 weeks), and 53 parent-term infant dyads, mean gestational age of 39 weeks (range of 36-42 weeks), from the Theirworld Edinburgh Birth Cohort were studied (www.tebc.ed.ac.uk). Parent-infant dyads were assessed at 9 months corrected (range of 8-10 months) for the preterm group and 9 months (range of 8-11 months) for the controls. 58 male infants and 42 female infants were included in analyses. Parents were video recorded for 10 minutes interacting with their child during play. Videos were coded for parental language and gesture using the novel coding scheme created during the course of this project. The Scottish Index of Multiple Deprivation 2016 (SIMD2016) rank was used to describe deprivation. Between group comparisons of parental gesture frequency were made using Student’s t-test, and the relationship between parental gesture and SIMD was evaluated using Pearson correlation. Multiple linear regression was used to investigate if parental language and gesture, prematurity, or family socioeconomic status had an effect on infant language outcomes at 24 months (measured using the MacArthur Bates CDI at 24 months corrected and the communication scores from the Vineland Adaptive Behaviour Scales). Findings from the parent child play showed no significant differences in the language and gesture used by parents of preterm infants vs. term infants during interaction. Socioeconomic status was associated with parental communication, and revealed that higher SIMD scores were positively correlated with word types, word tokens, and mean length of utterance. In other words, parents from a higher socioeconomic background spoke in longer sentences, with more words and with a more varied vocabulary. Examining relations over time, we found that parental communication at 9 months was not significantly related to language or communication at 24 months, while controlling for SES and gestational age. Due to a drop in sample size from 9 months (n=100) to 24 months (n=43), the robustness of this final analysis is limited.

In conclusion, this thesis has shown that socioeconomic deprivation has an effect on how parents communicate with their children during play in late infancy, and that this relationship is not directly influenced by gestational age at birth. The observation of socioeconomically related effects on parental language suggests that deprivation, and the increased rate of deprivation amongst the preterm population, may be a vital factor to consider when examining the increased risk of language delay within the preterm population. Further work, examining a larger sample of later infant language, is needed to increase our understanding of potentially important early predictors of language including gestational age, socioeconomic status, and parental language and gesture.