Table 1 Characteristics of overall sample

Maternal characteristics

Maternal age – mean ± SD [years]

31.98 ± 5.69

32.11 ± 5.95

31.91 ± 5.60

0.847

Nulliparous – n (%)

89 (67.4)

29 (65.9)

60 (68.2)

0.793

Placenta previa – n (%)

5 (3.8)

1 (2.3)

4 (4.5)

0.664

Chorioamnionitis – n (%)

6 (4.5)

0 (0.0)

6 (6.8)

0.191

Hypertension/preeclampsia – n (%)

56 (42.4)

32 (72.7)

24 (27.3)

< 0.001

HELLP syndrome – n (%)

14 (10.6)

8 (18.2)

6 (6.8)

0.069

Gestational diabetes – n (%)

16 (12.1)

3 (6.8)

13 (14.8)

0.187

Thrombophilia – n (%)

13 (9.8)

6 (13.6)

7 (8.0)

0.359

Autoimmune disease – n (%)

9 (6.8)

2 (4.5)

7 (8.0)

0.717

Smokers – n (%)

32 (24.2)

13 (29.5)

19 (21.6)

0.433

Education level – n (%)

0.689

 Lower secondary

 Upper secondary

 Tertiary

38 (28.8)

36 (27.3)

58 (43.9)

14 (31.8)

10 (22.7)

20 (45.5)

24 (27.3)

26 (29.5)

38 (43.2)

Perinatal characteristics

Pregnancy surveillance – n (%)

0.863

 Full

 Late onset

 No surveillance

125 (94.7)

5 (3.8)

2 (1.5)

42 (95.5)

2 (4.5)

0 (0.0)

83 (94.3)

3 (3.4)

2 (2.3)

Twin – n (%)

15 (11.4)

5 (11.4)

10 (11.4)

1.000

Antenatal corticosteroid – n (%)

109 (82.6)

38 (86.4)

71 (80.7)

0.417

Antenatal neuroprotection – n (%)

50 (37.9)

17 (38.6)

33 (37.5)

0.480

Labor induction – n (%)

84 (63.6)

44 (100)

40 (45.5)

< 0.001

PPRM – n (%)

20 (15.2)

0 (0.0)

20 (22.7)

0.002

Cesarean delivery – n (%)

98 (74.2)

44 (100)

54 (61.4)

< 0.001

Outborn – n (%)

9 (6.8)

0 (0.0)

9 (10.2)

0.069

Gestational age – mean ± SD [weeks]

29.13 ± 1.49

29.09 ± 1.36

29.15 ± 1.56

0.837

Birthweight – mean ± SD [gram]

1159.40 ± 334.21.

856.48 ± 201.66

1310.86 ± 280.14

< 0.001

Male – n (%)

69 (52.3)

21 (47.7)

48 (54.5)

0.460

5-minute Apgar score < 7 – n (%)

7 (5.3)

3 (6.8)

4 (4.5)

0.686

Endotracheal intubation – n (%)

28 (21.2)

13 (29.5)

15 (17.0)

0.098

Neonatal characteristics

CRIB score > 5 at admission – n (%)

24 (18.2)

21 (47.7)

3 (3.4)

< 0.001

Late-onset sepsis – n (%)

29 (22.0)

16 (36.4)

13 (14.8)

0.005

Hyaline membrane disease – n (%)

45 (34.1)

19 (43.2)

26 (29.5)

0.119

Bronchopulmonary dysplasia – n (%)

6 (4.5)

5 (11.4)

1 (1.1)

0.016

Pulmonary hemorrhage – n (%)

2 (1.5)

2 (4.5)

0 (0.0)

0.188

Patent arterial duct – n (%)

32 (24.2)

12 (27.3)

20 (22.7)

0.566

Hypotension – n (%)

9 (6.8)

5 (11.4)

4 (4.5)

0.159

Necrotizing enterocolitis – n (%)

3 (2.3)

2 (4.5)

1 (1.1)

0.258

ROP grade ≥ 3 – n (%)

4 (3.0)

3 (6.8)

1 (1.1)

0.108

PVL grade ≥ II – n (%)

5 (3.8)

1 (2.3)

4 (4.5)

0.664

PIVH grade III or PVHI – n (%)

6 (4.5)

0 (0.0)

6 (6.8)

0.191

Seizures – n (%)

2 (1.5)

0 (0.0)

2 (2.3)

0.842

Mechanical ventilation – n (%)

49 (37.1)

19 (43.2)

30 (34.1)

0.308

Postnatal surfactant – n (%)

45 (34.1)

19 (43.2)

26 (29.5)

0.119

Postnatal corticosteroids – n (%)

6 (4.5)

6 (13.6)

0 (0.0)

0.002