Demographic and clinical variables of infants ≥36 weeks gestational age with moderate or severe hypoxic-ischaemic encephalopathy both prepropensity and postpropensity score-matching
| Variables | Unmatched infants | Propensity score-matched infants | ||||||
| Born in non-CC | Born in CC | SMD | P value† | Born in non-CC | Born in CC | SMD | P value† | |
| n=2364* | n=2695* | n=2165* | n=2165* | |||||
| Gender (male) | 1354 (57.3) | 1417 (52.6) | −0.095 | 0.002 | 1203 (55.6) | 1225 (56.6) | 0.02 | 0.49 |
| Birth weight (g) | 3340 (2957–3760) | 3332 (2940–3750) | 0.014 | 0.7 | 3340 (2944–3760) | 3340 (2970–3775) | −0.018 | 0.23 |
| Gestation (weeks) | 40 (38–41) | 40 (38–41) | −0.015 | 0.47 | 40 (38–41) | 40 (38–41) | −0.006 | 0.85 |
| Birth year | 2014 (2012–2015) | 2014 (2012–2015) | −0.089 | 0.02 | 2014 (2012–2015) | 2014 (2012–2015) | 0.026 | 0.4 |
| Pre-eclampsia | 113 (4.8) | 120 (4.5) | 0.016 | 0.58 | 98 (4.5) | 97 (4.5) | 0.003 | 0.92 |
| Maternal infection | 555 (23.5) | 559 (20.7) | 0.066 | 0.02 | 480 (22.2) | 480 (22.2) | 0 | 0.99 |
| Mode of delivery‡ | ||||||||
| Em CS no labour | 405 (17.1) | 449 (16.7) | 0.013 | 0.66 | 375 (17.3) | 357 (16.5) | 0.022 | 0.48 |
| Em CS in labour | 682 (28.9) | 787 (29.2) | −0.008 | 0.78 | 639 (29.5) | 630 (29.1) | 0.008 | 0.8 |
| El CS no labour | 20 (0.9) | 28 (1.0) | −0.02 | 0.48 | 21 (0.95) | 18 (0.81) | 0.014 | 0.64 |
| El CS in labour | 7 (0.3) | 6 (0.2) | 0.014 | 0.61 | 7 (0.33) | 6 (0.27) | 0.011 | 0.72 |
| Instrumental | 358 (15.1) | 514 (19.1) | −0.104 | <0.001 | 355 (16.4) | 310 (14.3) | 0.06 | 0.05 |
| Missing | 100 (4.2) | 84 (3.1) | 0.059 | 0.04 | 80 (3.7) | 74 (3.4) | 0.014 | 0.65 |
| Presentation | ||||||||
| Cephalic | 1833 (77.5) | 2206 (81.9) | −0.107 | <0.001 | 1753 (81.0) | 1734 (80.1) | 0.022 | 0.47 |
| Breech | 154 (6.5) | 205 (7.6) | −0.043 | 0.13 | 142 (6.6) | 162 (7.5) | −0.036 | 0.2 |
| Transverse | 11 (0.5) | 12 (0.5) | 0.003 | 0.91 | 11 (0.62) | 11 (0.5) | 0.003 | 0.92 |
| Other | 20 (0.9) | 17 (0.6) | 0.025 | 0.37 | 15 (0.7) | 15 (0.68) | 0.004 | 0.9 |
| Missing | 346 (14.6) | 255 (9.5) | 0.16 | <0.001 | 244 (11.3) | 244 (11.3) | 0 | 1 |
| Intrapartum events | 276 (11.7) | 349 (13.0) | −0.039 | 0.17 | 265 (12.2) | 257 (11.9) | 0.011 | 0.72 |
| Significant resuscitation | 1364 (57.7) | 1703 (63.2) | −0.112 | <0.001 | 1312 (60.6) | 1278 (59.0) | 0.033 | 0.28 |
| Apgar at 5 min | 4 (2–5) | 4 (2–6) | −0.01 | 0.56 | 4 (2–5) | 4 (2–6) | −0.003 | 0.72 |
| Grade of HIE | ||||||||
| Grade 2 | 811 (34.3) | 1068 (39.6) | 0.11 | <0.001 | 779 (36.0) | 760 (35.1) | −0.018 | 0.55 |
| Grade 3 | 1553 (65.7) | 1627 (60.4) | 1386 (64.0) | 1405 (64.9) | ||||
| Place of birth level§ | ||||||||
| Level 1 | 670 (28.3) | 0 | – | 615 (28.4) | 0 | – | – | |
| Level 2 | 1546 (65.4) | 701 (26.0) | 0.861 | <0.001 | 1425 (65.8) | 566 (26.2) | 0.868 | <0.001 |
| Level 3 | 18 (0.8) | 1938 (71.9) | −2.198 | <0.001 | 16 (0.8) | 1551 (71.6) | −2.183 | <0.001 |
| Home | 96 (4.1) | 56 (2.1) | 0.094 | <0.001 | 82 (3.8) | 48 (2.2) | 0.094 | 0.002 |
| Midwife led unit | 34 (1.4) | 0 | – | 27 (1.2) | 0 | – | – | |
| Interhospital transfers§ | ||||||||
| L1–L3 transfer | 632 (26.7) | 0 | 0.854 | <0.001 | 578 (26.7) | 0 | – | <0.001 |
| L2–L3 transfer | 1386 (58.6) | 452 (16.8) | 0.957 | <0.001 | 1283 (59.3) | 358 (16.5) | 0.981 | <0.001 |
*Data are n (%) or median (IQR).
†Categorical data analysed using χ² test; non normally distributed continuous data analysed using Mann-Whitney U test; matched data by paired t-test for continuous data or McNemar’s test or extensions thereof for binary and categorical data.
‡Compared with baseline – NVD.
§Variables not included in propensity score matching.
CC, cooling centre; El CS, elective caesarean section; Em CS, emergency caesarean section; HIE, hypoxic-ischaemic encephalopathy; L2, level 2; L3, Level 3; NVD, normal vaginal delivery; SMD, Standardised mean difference.