Table 1.
Baseline characteristics of the NEC cohort and matched controls.
| Characteristic | Controls (n = 1,145) n (%) | NEC (n = 1,145)n (%) | P-value | Standardized difference |
|---|---|---|---|---|
| Infant characteristics | ||||
| Year of birth | 1.000 | 0.043 | ||
| 2006 | 123 (10.74%) | 123 (10.74%) | ||
| 2007 | 140 (12.23%) | 142 (12.40%) | ||
| 2008 | 145 (12.66%) | 143 (12.49%) | ||
| 2009 | 123 (10.74%) | 122 (10.66%) | ||
| 2010 | 108 (9.43%) | 109 (9.52%) | ||
| 2011 | 120 (10.48%) | 120 (10.48%) | ||
| 2012 | 133 (11.62%) | 133 (11.62%) | ||
| 2013 | 117 (10.22%) | 116 (10.13%) | ||
| 2014 | 136 (11.88%) | 137 (11.97%) | ||
| Sex | 0.966 | <0.001 | ||
| Male | 597 (52.14%) | 598 (52.23%) | ||
| Female | 548 (47.86%) | 547 (47.77%) | ||
| Multiple-births | 0.852 | −0.046 | ||
| No | 854 (74.59%) | 83 1 (72.58%) | ||
| Yes | 291 (25.41%) | 31 4 (27.42%) | ||
| Birth order | 0.705 | −0.016 | ||
| 1 | 640 (55.90%) | 631 (55.11%) | ||
| ≥ 2 | 505 (44.10%) | 514 (44.89%) | ||
| Gestational age at birth (weeks) | 0.728 | 0.026 | ||
| <24 | 12 (1.05%) | 11 (0.96%) | ||
| 24–36 | 917 (80.09%) | 932 (81.40%) | ||
| ≥37 | 216 (18.86%) | 202 (17.64%) | ||
| Birth weight (g) | 0.777 | 0.029 | ||
| <1,500 | 494 (43.14%) | 501 (43.76%) | ||
| 1,500–2,499 | 431 (37.64%) | 434 (37.90%) | ||
| 2,500–3,499 | 194 (16.94%) | 179 (15.63%) | ||
| ≥3,500 | 26 (2.27%) | 31 (2.71%) | ||
| Delivery method | 0.113 | −0.066 | ||
| Vaginal delivery | 464 (40.52%) | 427 (37.29%) | ||
| Cesarean section | 681 (59.48%) | 718 (62.71%) | ||
| PDA | 74(6.46%) | 150(13.1%) | <0.001 | 0.225 |
| IVH | 21(1.83%) | 44(3.84%) | 0.004 | 0.121 |
| Maternal characteristics | ||||
| Maternal age (Mean±SD) | 30.9 ± 4.8 | 31.1 ± 4.9 | 0.923 | 0.093 |
| 10–19 | 15 (1.31%) | 21 (1.83%) | ||
| 20–24 | 87 (7.60%) | 84 (7.34%) | ||
| 25–29 | 296 (25.85%) | 297 (25.94%) | ||
| 30–34 | 481 (42.01%) | 469 (40.96%) | ||
| 35–39 | 221 (19.30%) | 225 (19.65%) | ||
| ≥40 | 45 (3.93%) | 49 (4.28%) | ||
| Education level | 0.810 | 0.046 | ||
| Junior high school or lower | 61 (5.33%) | 71 (6.20%) | ||
| Senior high school | 457 (39.91%) | 446 (38.95%) | ||
| College | 547 (47.77%) | 551 (48.12%) | ||
| Master or above | 80 (6.99%) | 77 (6.72%) | ||
| Maternal disease history | ||||
| Hypertension | 149 (13.01%) | 138 (12.05%) | 0.488 | −0.029 |
| DM | 68 (5.94%) | 78 (6.81%) | 0.392 | 0.036 |
| Renal disease | 18 (1.57%) | 15 (1.31%) | 0.599 | −0.022 |
| Genitourinary infection | 94 (8.21%) | 98 (8.56%) | 0.763 | 0.013 |
| General infection | 18 (1.57%) | 21 (1.83%) | 0.628 | 0.020 |
| Anemia | 119 (10.39%) | 113 (9.87%) | 0.678 | −0.017 |
| Mental disorder | 37 (3.23%) | 41 (3.58%) | 0.645 | 0.019 |
| Asthma | 56 (4.89%) | 59 (5.15%) | 0.774 | 0.012 |
| Allergic rhinitis | 259 (22.62%) | 255 (22.27%) | 0.841 | −0.008 |
DM, diabetes mellitus; IVH, intraventricular hemorrhage;PDA, patent ductus arteriosus; SD, standard Deviation.