Shared book reading is a well-recognized facilitator for language development and reading achievement in preschoolers (1). The quantity of parent–child book reading between 1 and 2.5 years of age specifically predicts children's later receptive vocabulary, reading comprehension, and internal motivation to read (2). The American Academy of Pediatrics issued a policy statement recommending parent–child home reading beginning in early childhood (3). Over the last decades several public-health interventions were developed to encourage parents to do so, both in general populations and in low-income families (e.g., the Reach Out and Read program, the Bedside Reading program) (4, 5).

Empirical evidence from longitudinal and intervention studies suggests that reading to preverbal children may be at least as important for long-term child outcomes. Farrant and Zubrick (6) used data from The Longitudinal Study of Australian Children to assess the effect of early storybook reading during the first year to later socio-cognitive development. The authors found that the effect of maternal education on children's vocabulary development at 34 months of age was completely mediated by the level of parent–child book reading. Brown et al. (7) compared the effectiveness of a high- and a low-intensity of shared reading interventions for 32 parent–child dyads with typically developing babies 3- to 12-months-of-age (high vs. low-intensity). Increased performance in the high-intensity group was observed for language scores and social communication scores immediately post-intervention and at 2-years-of-age. On this ground, recommendations for the parents to read aloud to their children has been extended to those as young as 2 weeks (3, 8). Other programs were developed to be provided by nurses beginning at childbirth (e.g., “Let's Read”, “Better Beginnings”) (9, 10).

Several studies have explored the mechanisms underpinning the effectiveness of shared parental reading on typically developing children.

The exposition of children to enriched language, through exposition to more grammatically enriched linguistic input, is regarded as a central point for the effectiveness of parental reading interventions (2). Weisleder and Fernald (11) demonstrated that the processing speed is affected by the amount of language a child hears, ultimately affecting the acquisition of vocabulary later. In addition, the language used in books is far richer than the language of everyday speech (12). Noble et al. (13) showed that the child-directed speech generated by shared book reading contains significantly more grammatically rich constructions than child-directed speech generated by toy play.

Non-linguistic components of the shared reading sessions could also play an important role in the effectiveness of these interventions. Shared parent–infant reading sessions tend to elicit more interactive communication between infant and caregiver including more frequent verbal responses, eye-contact, touch and feel (14). In this, shared book reading could provide a context for caregivers to provide affective support and enriched communication (15). The meta-analysis conducted by Xie et al. (16) found that shared reading interventions are associated with increased parent–child relationships.

To discriminate the effect of language exposure from other aspects of the communication some studies compared the effect of straight reading to responsive/interactive reading. Most of these reports showed that live reading are more beneficial for children in increasing their language abilities compared to recorded reading (17, 18), while another study found no significant difference (19).

Guide for reading sessions often includes parental advice of paying particular attention to infant social cues. Warm and sensitive parental interactions during the reading sessions are regarded as an important aspect to explain the potential benefit of parent–infant reading sessions. A randomized controlled trial demonstrated that after receiving an 8-week shared reading intervention, parents showed increased sensitivity, elaboration, and reciprocity during shared reading interactions with their infants compared with the control group (20).

In addition to infant-parent interactions, reduced parental anxiety is regarded as a significant mediator of the effect of reading interventions. A. Weisleder et al. (21) conducted a secondary analysis of data from a randomized controlled trial comparing the effect of interactive parental guidance based on play or shared reading. The authors found that decreased parental stress was an independent mediator for the effect of shared reading sessions on behavioral outcomes at 36 months. Interestingly, several longitudinal studies have also supported a link between less parenting stress and increased frequency and quality of shared reading (22–24). Other authors have stressed the importance of considering other parental characteristics, such as harsh parenting that is negatively associated with early shared reading (25).

Prematurity is a well-known risk factor for neurocognitive impairments. Half of premature infants would have mild-to-moderate cognitive impairments, including language and related learning disorders (26), and one out of five would suffer from severe disabilities (27). Associated medical conditions (e.g., cerebral palsy, sensory impairment) contribute to the observed increased risk for cognitive and language impairment among these children (28).

Prematurity is also a medical context associated with an increased risk of attachment issue (29). The birth of a premature infant is generally associated with a constellation of risk factors contributing to less synchronous and contingent caregiver-infant interactions. These factors can be roughly defined as predominantly involving (i) the early infant's aptitude of communicate, (ii) the parental aptitudes to provide well-adapted interactions based on infant social cues, (iii) and the environmental context providing less opportunity for repeated interactive patterns and ill-adapted sensory stimulation for the developmental age (30, 31). In practice such risk factors co-occur and influence mutually increasing parents' difficulties to connect with their child and vice-versa. Guidelines of good practices for preterm infant care in neonatal intensive care units (NICU) highlight the importance of promoting a high level of parental involvement to reduce the risk of insecure attachment. This involves programs aiming to reduce parental stress, to improve parental sensitivity to infant social signals and to promote attuned parenting.

Considering the importance of early sound exposure to cerebral development and the neural immaturity of preterm infants, much attention has been devoted to infants' sound environment in the days following childbirth (32–34). The brain's structural connectivity and auditory function of premature infants are known to be affected by the exposure to parental speech (35, 36). Compared to a home setting, the NICU is an environment with less opportunity of language exposure with frequent unpredictable sounds (37). Some have wondered whether a deprivation of exposure to parental voice and of caregivers-to-infants communication in an NICE could alter neurodevelopmental and emotional outcomes. Caskey et al. (32) found a positive relation between the amounts of language exposure using a Language Environment Analysis (LENA) device in an NICU, and improvements in neurodevelopmental language testing at 7 and 18 months among those infants.

Early interventions, such as shared reading interventions, that promote both exposure to parental voice and the opportunity of richer parents-infant interactions are therefore worth considering in preterm infants to improve long-term neurodevelopmental and emotional outcomes (38).

The principle of shared book reading sessions in an NICU was presented in a seminal article by Jones and Englestad (39). More recently, two articles described the implementation of shared book reading interventions in an NICU in Italy (40) and in the USA (41) (Table 1). Of note, parent–infant shared reading programs described here do not involve interventions provided by dedicated psychotherapists.

Lariviere and Rennick (42) described the experiences of parents involved in a shared book reading intervention in an NICU in Canada with 59 infants. The nurses advised the parents to read a few minutes every day from a book previously selected among the ward library and personalized. Authors reported that 86% of parents involved in reading sessions found the activity enjoyable, and 69% mentioned it helped them to feel closer to their baby. Comparing this to a historical control group, parents involved in this activity were twice as many to report reading three or more times a week to their infants 3 months post NICU discharge (56 vs. 23%).

Biasini et al. (47) replicated this finding among 49 Italian preterm infants compared to 27 subjects in the historical control group. The authors found that a large majority of parents enjoyed reading sessions and most of them felt it helped them feel closer to their babies. The intervention was associated with higher Hearing and Language subscore of the GMDS at 18th month of follow-up.

Scala et al. (43) examined the effect of parental shared reading intervention on preterm infant's physiological parameters (n = 18 dyads). Parents read a book to infants in their incubator via Bluetooth speakers. Oxygen desaturation decreased during parental reading compared to baseline (3 and 1 h before). This effect persisted up to 1 h after reading exposure. Interestingly, exploratory analyses showed that the effect was stronger for live compared to previously recorded reading sessions and for maternal compared to paternal sessions.

Neri et al. (44) compared the development of language acquisition during the first 24 months following the birth between preterm infants who had parental shared book reading session in an NICU (n = 55) and a historical control group (n = 45). Authors found no significant difference in language scores of the Griffiths Mental Development Scales-Revised between the two groups at 24 months. However, the analysis of developmental trajectories based on intermediary scores (at 3, 6, 9, 12, 18 months) showed that the decline in language skill observed among all participants compared to expected scores in general population was significantly reduced in the reading group compared to controls.

Braid and Bernstein (45) used data from a large community-based birth cohort to examine in a sample of preterm children (N = 1,400) the association between parental shared book reading and children's cognitive development. The authors found that reading aloud at least three times a week was associated with higher Bayley Mental Scale T-scores in 2-year-old preterm children. The relation remained statistically significant after controlling on covariables related to neonatal and maternal characteristics [β = 2.7, 95% (CI 1.1, 4.3), p < 0.001].

Zuccarini et al. (46) determined the effectiveness of a speech intervention for late talkers aged 2–3 years. The intervention focused on shared reading sessions by parents at home and involved more technical aspects such interactive guidance based on video feedback. The authors noted a stronger improvement in expressive syntactic skills 6 months later after the intervention in subjects in the intervention group (n = 17) compared to those in the control group (n = 6). No significant difference was found between the two groups with regards to expressive lexical skills.

Preliminary evidence supports the benefit of shared reading intervention in premature infants to support language acquisition and parental bonding. Such programs are feasible and well-accepted in an NICU. Structured clinical trials are now needed to confirm these preliminary findings. The question also remains about which components of shared reading interventions mediates its effectiveness. Answering this could help to better articulate it to preexisting interventions supporting cognitive stimulation and good parenting in premature infants. It would also help to define the group of patients for whom this may be particularly relevant.

XB, LB, J-MG, FW, PC, SV-S, and CM: study concept, design, and interpretation of data. XB and LB: acquisition of data and drafting the manuscript. J-MG, FW, PC, SV-S, and CM: critical revision of the manuscript for important intellectual content. All authors: final draft. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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