| US-Guided (n = 23) | Non-US Guided (n = 36) | P-value | |
|---|---|---|---|
| Weight (g), mean (SD) | 3100 (1044) | 1915 (1193) | <0.001 |
| Postmenstrual age (weeks), mean (SD) | 38.4 (3.8) | 34.3 (6.3) | 0.007 |
| Number of attempts, mean (SD) | 1.4 (0.6) | 2.2 (1.4) | 0.01 |
| First attempt success, n (%) | 14 (60.9%) | 14 (38.9%) | 0.10 |