TABLE 1

Characteristics of Study Cohort

Gestational Age
22 Weeks (n = 75)23 Weeks (n = 245)24 Weeks (n = 332)25 Weeks (n = 405)Total N =1057
Demographic and perinatal characteristics
 BW, mean ± SD, g488 ± 72575 ± 80634 ± 103741 ± 137651 ± 137
 BW <400 g, n/N (%)7/75 (9.3)3/245(1.2)7/332(2.1)9/405(2.2)26/1057 (2.5)
 Male, n/N (%)32/75 (42.7)133/244a (54.5)163/332 (49.1)219/403a (54.3)547/1054a (51.9)
 Multiple birth, n/N (%)16/75 (21.3)60/245 (24.5)61/332 (18.4)82/405 (20.2)219/1057 (20.7)
 Preterm rupture of membranes, n/N (%)36/75 (48.0)96/245 (39.2)140/332 (42.2)148/405 (36.5)420/1057 (39.7)
 Antenatal steroid use, n/N (%)16/75 (21.3)79/245 (32.2)137/332 (41.3)177/405 (43.7)409/1057 (38.7)
 Maternal transport, n/N (%)38/75 (50.7)151/245 (61.6)207/331a (62.5)247/402a (61.4)643/1053a (61.1)
 Outborn, n/N (%)6/75 (8.0)20/245 (8.2)31/332 (9.3)41/405 (10.1)98/1057 (9.3)
 Cesarean delivery, n/N (%)18/75 (24.0)104/245 (42.4)218/332 (65.7)297/405 (73.3)637/1057 (60.3)
In-hospital morbidities and interventions, n/N (%)
 RDS diagnosed60/74a (81.1)191/245 (78.0)251/332 (75.6)309/405 (76.3)811/1056a (76.8)
 CLD at 36 weeksb15/71a (21.1)71/236a (30.1)121/319a (37.9)133/392a (33.9)340/1018a (33.4)
 PDA ligation4/72a (5.6)34/238a (14.3)50/316a (15.8)41/389a (10.5)129/1015a (12.7)
 Neonatal seizure11/74a (14.9)28/245 (11.4)40/331a (12.1)30/405 (7.4)109/1055a (10.3)
 IVH grade 3–418/74a (24.3)52/241a (21.6)48/328a (14.6)49/403a (12.2)167/1046a (16.0)
 Cystic PVL2/74a (2.7)10/244a (4.1)13/331a (3.9)22/405 (5.4)47/1054a (4.5)
 Sepsis17/74a (23.0)58/244a (23.8)73/331a (22.1)59/405 (14.6)207/1054a (19.6)
 Necrotizing enterocolitis1/74a (1.4)16/245 (6.5)10/331a (3.0)15/405 (3.7)42/1055a (4.0)
 ROP requiring treatment15/75a (20.0)73/245 (29.8)102/331a (30.8)128/405 (31.6)318/1056a (30.1)
  • BW, birth weight; PDA, patent ductus arteriosus; PVL, periventricular leukomalacia; RDS, respiratory distress syndrome.

  • a There were cases without data on this characteristic.

  • b CLD at 36 weeks was defined when an infant received supplemental oxygen at the postmenstrual age of 36 weeks.