Mean gestational age (GA) in weeks and mean birth weight (BW) in grams (g) of infants studied in period 1 and period 2
| Period 1 | Period 2 | p Value | |
| 22 0/7–22 6/7 weeks | |||
| n | 7 | 10 | |
| GA in weeks, mean (SD) | 22.3 (0.2) | 22.5 (0.6) | 0.37 |
| BW in g, mean (SD) | 508 (72) | 505 (132) | 0.97 |
| 23 0/7–23 6/7 weeks | |||
| n | 29 | 37 | |
| GA in weeks, mean (SD) | 23.6 (0.4) | 23.6 (0.3) | 0.69 |
| BW in g, mean (SD) | 564 (101) | 639 (110) | 0.007 |
| 24 0/7–24 6/7 weeks | |||
| n | 69 | 58 | |
| GA in weeks, mean (SD) | 24.5 (0.3) | 24.4 (0.3) | 0.59 |
| BW in g, mean (SD) | 704 (131) | 670 (94) | 0.11 |
| 25 0/7–25 6/7 weeks | |||
| n | 115 | 99 | |
| GA in weeks, mean (SD) | 25.4 (0.3) | 25.4 (0.3) | 0.36 |
| BW in g, mean (SD) | 734 (125) | 771 (98) | 0.05 |
SD, standard deviation.