Table 3 Subgroup analysis by singleton pregnancy

 APGAR score < 7 (1 min)

269 (17.0%)

96 (14.3%)

140 (17.9%)

33 (25.6%)

0.005^ab

0.777 (0.584–1.034)

1.499 (0.962–2.336)

 APGAR score < 7 (5 min)

78 (4.9%)

33 (4.9%)

35 (4.5%)

10 (7.8%)

0.279

1.139 (0.697–1.859)

1.899 (0.907–3.976)

 Post-natal adaptation

66 (4.2%)

23 (3.4%)

39 (5.0%)

4 (3.1%)

0.271

0.703 (0.414–1.193)

0.627 (0.219–1.799)

 Bronchopulmonary dysplasia

45 (2.8%)

18 (2.7%)

22 (2.8%)

5 (3.9%)

0.752

0.929 (0.487–1.769)

1.376 (0.504–3.761)

 Pneumonia

54 (3.4%)

15 (2.2%)

29 (3.7%)

10 (7.8%)

0.005^ab

0.609 (0.322–1.148)

2.516 (1.179–5.371)

 Pneumothorax

30 (1.9%)

9 (1.3%)

19 (2.4%)

2 (1.6%)

0.301

0.552 (0.247–1.237)

0.757 (0.173–3.324)

 Intraventricular haemorrhage

61 (3.8%)

23 (3.4%)

29 (3.7%)

9 (7.0%)

0.15

0.908 (0.515–1.600)

1.838 (0.840–4.023)

 Necrotising enterocolitis

45 (2.8%)

12 (1.8%)

28 (3.6%)

5 (3.9%)

0.041^c

0.515 (0.258–0.982)

1.002 (0.372–2.701)

 Neonatal death

34 (2.1%)

14 (2.1%)

16 (2.0%)

4 (3.1%)

0.736

0.997 (0.479–2.076)

1.569 (0.504–4.884)

 Sepsis

145 (9.1%)

48 (7.1%)

76 (9.7%)

21 (16.3%)

0.003^ab

0.729 (0.499–1.065)

1.785 (1.050–3.034)

 Hypothermia

41 (2.6%)

17 (2.5%)

18 (2.3%)

6 (4.7%)

0.294

1.144 (0.582–2.247)

2.033 (0.778–5.311)

 Phototherapy

917 (57.9%)

370 (55.0%)

450 (57.5%)

97 (75.2%)

<  0.001^ab

0.928 (0.752–1.145)

2.180 (1.420–3.349)

 Transient tachypnoea of the newborn

344 (21.7%)

141 (21.0%)

163 (20.8%)

40 (31.0%)

0.028^ab

1.001 (0.775–1.292)

1.719 (1.134–2.606)

 Ventilator support

194 (12.2%)

89 (13.2%)

82 (10.5%)

23 (17.8%)

0.036^a

1.281 (0.928–1.768)

1.861 (1.115–3.107)

 Continuous positive airway pressure

320 (20.2%)

117 (17.4%)

166 (21.2%)

37 (28.7%)

0.008^b

0.786 (0.603–1.025)

1.448 (0.948–2.210)

 Positive pressure ventilation

201 (12.7%)

88 (13.1%)

86 (11.0%)

27 (20.9%)

0.007^a

1.257 (0.912–1.731)

2.140 (1.313–3.486)

 Intermediate care unit admission

1107 (69.8%)

491 (73.0%)

549 (70.1%)

67 (51.9%)

<  0.001^ab

1.137 (0.903–1.432)

0.474 (0.323–0.695)

 Neonatal intensive care unit admission

344 (21.7%)

133 (19.8%)

164 (20.9%)

47 (36.4%)

<  0.001^ab

0.946 (0.730–1.225)

2.160 (1.444–3.232)

 Respiratory distress syndrome

72 (4.5%)

34 (5.1%)

29 (3.7%)

9 (7.0%)

0.179

1.372 (0.824–2.283)

1.776 (0.812–3.886)

 Persistent tachypnoea of the newborn

1 (0.1%)

1 (0.1%)

0 (0.0%)

0 (0.0%)

0.508

–

–

 Length of hospital stay (days)

7 (1–179)

6 (1–179)

7 (1–179)

14 (1–179)

<  0.001^abc

–

–

 Mean neonatal weight (grams)

2245.5 ± 568.5

2327.9 ± 573.6

2219.1 ± 556.7

1975.6 ± 515.3

<  0.001^abc

–

–

Maternal

–

–

 Gestational age at delivery (weeks of gestation)

34.5 ± 2.1

34.8 ± 2.0

34.4 ± 2.1

33.4 ± 2.0

<  0.001^abc

–

–

 Diabetes mellitus (DM)

28 (1.8%)

11 (1.6%)

14 (1.8%)

3 (2.3%)

0.842

0.913 (0.412–2.204)

1.308 (0.371–4.616)

 Hypertension

102 (6.4%)

37 (5.5%)

45 (5.7%)

20 (15.5%)

< 0.001^ab

0.954 (0.610–1.493)

3.009 (1.712–5.288)

 Others

153 (9.7%)

55 (8.2%)

78 (10.0%)

20 (15.5%)

0.034^b

0.804 (0.560–1.155)

1.658 (0.975–2.821)

Length of hospital stay (days)

6 (2–143)

5 (2–31)

7 (2–56)

12 (2–143)

<  0.001^abc

–

–

Puerperal infection

11 (0.7%)

5 (0.7%)

5 (0.6%)

1 (0.8%)

0.965

1.165 (0.336–4.040)

1.216 (0.141–10.490)

Referral to other centres

21 (1.3%)

5 (0.7%)

13 (1.7%)

3 (2.3%)

0.182

0.443 (0.157–1.250)

1.410 (0.396–5.019)