Baseline demographics of the study groups
| Variable | Catheter group (N=16) | Opioid group (N=14) |
| Gestation, weeks, median (IQR) | 38 (38–39) | 38 (37–39) |
| Male, N (%) | 10 (63 %) | 9 (64 %) |
| Birth weight, g, median (IQR) | 3250 (2965–3570) | 3133 (2820–3601) |
| Primary diagnosis, N (%) | ||
| Congenital diaphragmatic hernia | 8 (50 %) | 7 (50 %) |
| Malrotation/volvulus | 2 (13 %) | 1 (7 %) |
| Bowel atresia | 4 (25 %) | 5 (33 %) |
| Other | 2 (13 %) | 1 (7 %) |
| Day of life underwent surgery, days, median (IQR) | 2.5 (2, 4.5) | 4.0 (2,6) |
| Opioids before surgery, N (%) | 8 (50 %) | 9 (64 %) |
| Cumulative intravenous opioid before surgery, µg/kg, median (IQR) | 442 (0–815) | 372.0 (0–665) |