Participants
POLAND
We recruited participants from 8 NICUs (7 level III and 1 level IV) in Argentina, Colombia, Israel, Norway, and Poland, countries where social systems enable continual parental presence during infant hospitalization. Preterm infants that were born at less than 35 weeks’ gestational age, were likely to be hospitalized a minimum 2 weeks from inclusion, and had been declared by NICU staff as medically stable to start MT (typically after 26 weeks’ postmenstrual age) were eligible for enrollment if they had parents who (1) provided written, site-specific informed consent, (2) were willing to engage in at least 2 of 3 MT sessions per week, (3) possessed sufficient understanding of the respective national language(s) to answer questionnaires and participate in MT, and (4) possessed sufficient mental capacity to complete the intervention and questionnaires.