Baseline characteristics
| Characteristic | Nadir platelet count (×109/L) | |||||||||
| Overall (n=2772) | <10 (n=6) | 10–24 (n=51) | 25–49 (n=174) | 50–99 (n=377) | 100–149 (n=537) | 150–199 (n=626) | 200–249 (n=555) | 250–299 (n=306) | ≥300 (n=140) | |
| GA at birth, median (IQR), weeks | 29 (27–30) | 29 (27–30) | 28 (27–30) | 28 (27–30) | 28 (27–30) | 29 (27–30) | 29 (27–31) | 30 (28–31) | 30 (28–31) | 30 (28–31) |
| Male sex, n (%) | 1478 (53) | 4 (67) | 25 (49) | 103 (59) | 208 (55) | 287 (54) | 356 (57) | 293 (53) | 139 (45) | 63 (45) |
| Birth weight, mean ±SD, g | 1236 ±367 | 1627 ±834 | 962 ±355 | 977 ±318 | 1048 ±314 | 1166 ±343 | 1261 ±346 | 1366 ±338 | 1390 ±334 | 1454 ±354 |
| SGA, n (%) | 926 (33) | 2 (33) | 34 (67) | 116 (67) | 192 (51) | 204 (38) | 188 (30) | 109 (20) | 65 (21) | 16 (11) |
| Caesarean section, n (%) | 1399 (51) | 6 (100) | 37 (73) | 139 (80) | 228 (61) | 301 (56) | 298 (48) | 234 (42) | 111 (36) | 45 (32) |
| Twin pregnancy, n (%) | 1127 (41) | 0 (0) | 11 (22) | 61 (35) | 135 (36) | 240 (45) | 274 (44) | 239 (43) | 121 (40) | 46 (33) |
| Birth asphyxia, n (%) | 55 (2) | 1 (17) | 1 (2) | 8 (5) | 11 (3) | 16 (3) | 9 (1) | 5 (1) | 4 (1) | 0 (0) |
| Mechanical ventilation, n (%) | 1241 (45) | 6 (100) | 43 (84) | 123 (71) | 238 (63) | 305 (57) | 247 (40) | 182 (33) | 68 (22) | 29 (21) |
| Sepsis,* n (%) | 715 (26) | 4 (67) | 28 (55) | 81 (47) | 146 (39) | 178 (33) | 133 (21) | 80 (14) | 50 (16) | 15 (11) |
| NEC,† n (%) | 117 (4) | 0 (0) | 7 (14) | 13 (8) | 22 (6) | 24 (5) | 24 (4) | 20 (4) | 6 (2) | 1 (1) |
| Inotropes, n (%) | 382 (14) | 3 (50) | 14 (28) | 59 (34) | 92 (24) | 95 (18) | 68 (11) | 38 (7) | 8 (3) | 5 (4) |
| Major congenital malformation,‡ n (%) | 90 (3) | 2 (33) | 4 (8) | 5 (3) | 19 (5) | 23 (4) | 11 (2) | 14 (3) | 11 (4) | 1 (1) |
| Number of PLT transfusions per infant,§ median (IQR), n | 1 (1–2) (n=181) | 3 (3–5) (n=4) | 2 (1–3) (n=50) | 1 (1–2) (n=104) | 1 (1–2) (n=20) | 1 (1–1) (n=1) | 0 (n=0) | 1 (1–1) (n=2) | 0 (n=0) | 0 (n=0) |
| Postnatal age at nadir,¶ median (IQR), days | 2 (1–3) | 6 (1–13) | 5 (3–10) | 4 (2–6) | 3 (2–5) | 2 (1–4) | 1 (1–3) | 1 (1–2) | 1 (1–2) | 1 (1–1) |
| Length of NICU stay, median (IQR), days | 13 (6–29) | 11 (6–42) | 19 (11–43) | 23 (11–43) | 21 (10–39) | 18 (8–35) | 12 (6–26) | 10 (5–23) | 8 (4–16) | 8 (4–17) |
*Culture-positive sepsis.
†NEC ≥grade IIA as per Bell’s criteria.
‡Congenital malformation associated with a poor prognosis or life-threatening condition.
§Number of prophylactic platelet transfusions (after the nadir) per transfused infant. The transfusion indications in the group of 100–149×109/L (n=1) and 200–249×109/L (n=2) were resuscitation setting and cardiac surgery, respectively.
¶The first 24 hours after birth are counted as day 1.
GA, gestational age; NEC, necrotising enterocolitis; NICU, neonatal intensive care unit; PLT, platelet; SGA, small-for-gestational age (birth weight <p10).