The NIPS scale is a validated 6-indicator scale for the assessment of acute pain in neonates11,13. It measure movement of arms and legs, breathing patterns, cry, facial expression and state of arousal. Score ranges from 0 (no pain) to 7 (severe pain). NIPS score <4 means no pain-mild pain. NIPS score ≥4 means moderate-severe pain. NIPS score was measured at three time points: NIPS0 (2 minutes before sampling); NIPS1 (the highest value of the scale in the first 10 seconds after heel prick); and NIPS2 (2 minutes after the procedure). NIPS2 was not recorded if sampling had not finished at this time point. This took place in one newborn (2,8%) of group 1, five (14,2%), six (18.1%), and five (15.1%) of group 2, 3 and 4 respectively. NIPS was measured by three researchers who watched the videos: one expert neonatologist (Observer 1) and two young paediatricians (Observers 2 and 3). Coincidence was 90.8% (95% CI 87.8-93.8) between observers 1 and 2; 75% (70.5-79.5) between observers 1 and 3; and 78.7% (74.7-82.9) between observers 2 and 3. Consequently, only data of the expert neonatologist is shown.