Patient-Reported Outcomes Measurement Information System (PROMIS) 8a Higher scores indicate higher levels of depression: T-score: standardized score mean of 50 and standard deviation (SD) of 10 The T-score is a score on a scale where 50 represents the average for the US general population (minimum of 8a Short Form is 38.2, maximum is 81.3). Each 10-point change represents one standard deviation (SD). A T-score of 75 or greater indicates clinically significant, severe symptoms.

The percent of videos mothers watched were controlled in our analyses showing data trends as change scores. At each follow-up time point [14 days post-baseline (T2), 28 days post-baseline (T3), and 30 days after infant discharge from the NICU (T4)], we computed mean differences and 95% CI between groups to evaluate trends in outcomes. Reported here are mean (SE) in change scores from Baseline to 30 days after infant discharge from the NICU (T4).

Patient-Reported Outcomes Measurement Information System (PROMIS) 8a Higher scores indicate higher levels of anxiety: T-score: standardized score mean of 50 and standard deviation (SD) of 10 The T-score is a score on a scale where 50 represents the average for the US general population (minimum of 8a Short Form is 38.2, maximum is 81.3). Each 10-point change represents one standard deviation (SD). A T-score of 75 or greater indicates clinically significant, severe symptoms.

The percent of videos mothers watched were controlled in our analyses showing data trends as change scores. At each follow-up time point [14 days post-baseline (T2), 28 days post-baseline (T3), and 30 days after infant discharge from the NICU (T4)], we computed mean differences and 95% CI between groups to evaluate trends in outcomes. Reported here are mean (SE) in change scores from Baseline at each time point in the study.

Number of infants receiving exclusive mother's milk were recorded and percent of infants was calculated from the total number number of infants receiving enteral feeds. Infants were marked as receiving exclusive mother's milk if all feeds were mother's milk (i.e., infant did not receive donor milk or formula).

Percent of infants receiving exclusive mother's milk = Number of infants receiving exclusive mother's milk / Number of infants on enteral feeds

Assessed at Baseline, 14 days post-baseline (T2), 28 days post-baseline (T3).

Change in Z score weight from birth to 36 weeks corrected gestational age (or at discharge if earlier) was calculated using PediTools Fenton 2013 Growth Calculator for Preterm Infants. Z-scores are the number of standard deviations above or below a growth chart's center (mean) curve. A Fenton preterm growth chart Z-score of 0 means the infant's growth measurement (e.g., weight) is at the average (mean) for their age and sex. Changes in Z-scores tell if a second measurement is closer or further away from the growth chart center than the previous measurement. Change in Z-score of 0 means the infant's percentile on the growth chart did not change. Higher Z scores indicate increased growth acceleration. The Academy of Nutrition and Dietetics considers Z score changes less than -0.8 to indicate growth failure. Normal growth during NICU hospitalization is defined as a z-score change of -0.79 to 0.79.

Z score Δ = [Zscore at 36 weeks corrected gestational age] - [Zscore at birth]

Z score Δ = [Zscore at 36 weeks corrected gestational age] - [Zscore at birth]

Days of NICU hospitalization (calculated from days between date of birth to date of discharge from NICU)

The infant's electronic health record was reviewed for hospital readmissions and emergency department visits within 30 days of infant discharge. Mothers were also asked "Did your infant have any re-hospitalizations or emergency department visits within 30 days of discharge?", to ensure all rehospitalizations and ED visits were captured.

Coded as Yes/No and extracted from the infant's electronic health record. Mothers were also asked "Did your infant have any re-hospitalizations or emergency department visits within 30 days of discharge?", to ensure all rehospitalizations and ED visits were captured.