Table 1: Comparison of selected demographic data in the studied cohorts.

Extremely preterm (23–26 weeks) ( )Very preterm (27–29 weeks) ( )Moderately preterm (30–32 weeks) ( )

Birth weight, g ( ) <0.001a
Gestational age (weeks) ( ) <0.001a
Male gender24 (58%)20 (51%)17 (52%)0.76b
Vaginal delivery/Cesarean section20/2115/248/250.01b
Multiple pregnancy4 (10%)8 (20%)6 (18%)0.56b
Small-for-gestational-age infant4 (10%)1 (2%) 5 (15%)0.1b
Maternal hypertension8 (19%)7 (18%)2 (8%)0.74b
Maternal diabetes3 (7%)2 (5%)00.79b
Maternal fever/infection prior to delivery5 (12%)6 (15%)4 (13%)0.8b
1st minute Apgar score (Me; 25–75th percentile)2 (1–4)5 (4–6)5 (2–6)0.01c
5th minute Apgar score (Me; 25–75th percentile)6 (4–6)7 (6-7)7 (6–8)0.001c
Delivery room intubation28 (69%) 16 (40%)11 (33%)0.01b
Surfactant therapy 33 (81%)29 (73%)14 (43%)0.003b
Initial a/A ratio 0.01a
Prenatal steroids10 (25%)12 (29%)22 (66%)0.01b
Ureaplasma infection12 (29%)8 (21%)6 (18%)0.28b
Pharmacological closure of patent ductus arteriosus22 (54%)23 (59%)11 (33%)0.08b
Surgical closure of patent ductus arteriosus18 (44%)4 (10%)2 (6%)<0.001b
Length of mechanical ventilation (Me; 25–75th percentile)42 (25–52)3 (1–10)2 (0–6)<0.001c
Bronchopulmonary dysplasia40 (98%)24 (62%)6 (18%)<0.001b

value for one-way analysis of variance.
value for chi-square test.
value for Kruskal-Wallis analysis of variance.