Aim: This longitudinal study investigated associations between language environment and parent-infant close contact in the neonatal intensive care unit (NICU) and preterm children's lexical abilities.

Methods: NICU language environment of 43 very preterm infants (born < 32 gestational weeks) was measured with the Language Environment Analysis System (LENA; variables: number of adult words, conversational turns, and child vocalisations). Parent-infant close contact (holding and skin-to-skin contact) in the NICU was reported using parental closeness diaries. At 15 and 18 months' corrected age, lexical development was measured with screening methods, and eye tracking-based lexical processing was assessed at 18 months. N varied between 29 and 38 in different outcome measures.

Results: LENA measured conversational turns and child vocalisations, and parent-infant close contact associated positively with lexical development (r = 0.35-0.57). High numbers of NICU adult words associated negatively with lexical processing (r = -0.38- -0.40). In regression models, conversational turns and parent-infant close contact explained 34%-35% of receptive development.

Conclusion: Findings suggest that adult-infant turn taking and parent-infant close contact in the NICU are positively associated with lexical development. High numbers of overheard words in the NICU may not favour later lexical processing. Further research is warranted on the significance of NICU language environment on later lexical abilities.