Researchers hypothesised that preterm infants exposed to higher word counts would have higher cognitive and language scores at seven and 18 months corrected age.
"Our earlier study identified that extremely premature infants vocalise (make sounds) eight weeks before their mother's due date and vocalise more when their mothers are present in the NICU than when they are cared for by NICU (neonatal intensive care unit) staff," said Betty Vohr, director of Women & Infants Hospital's Neonatal Follow-Up Programme.
At 32 weeks and 36 weeks, staff recorded the NICU environment for 16 hours with a Language Environment Analysis (LENA) microprocessor.
"The follow-up of these infants has revealed that the adult word count to which infants are exposed in the NICU at 32 and 36 weeks predicts their language and cognitive scores at 18 months.
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"Every increase by 100 adult words per hour during the 32 week LENA recording was associated with a two point increase in the language score at 18 months," said Vohr.
"Our study demonstrates the powerful impact of parents visiting and talking to their infants in the NICU on their developmental outcomes.
The study was published in the journal Pediatrics.