Table 1.
Infant Characteristics, Medical Conditions, and Therapies.
| Variable | Epoch 1 (2000–2003) |
Epoch 2 (2004–2007) |
Epoch 3 (2008–2011) |
P Value* |
|---|---|---|---|---|
| All infants | ||||
| Total no. in cohort | 1391 | 1535 | 1348 | |
| Median birth weight (interquartile range) — g | 600 (533–670) | 590 (520–670) | 595 (511–680) | 0.11 |
| Gestational age at birth — no./total no. (%) | ||||
| 22 wk | 241/1391 (17) | 274/1535 (18) | 234/1348 (17) | 0.92 |
| 23 wk | 496/1391 (36) | 489/1535 (32) | 450/1348 (33) | 0.09 |
| 24 wk | 654/1391 (47) | 772/1535 (50) | 664/1348 (49) | 0.20 |
| Small for gestational age — no./total no. (%) | 39/1391 (3) | 65/1535 (4) | 105/1347 (8) | <0.001 |
| Male sex — no./total no. (%) | 759/1391 (55) | 834/1535 (54) | 702/1348 (52) | 0.35 |
| Race — no./total no. (%)† | ||||
| Black | 642/1385 (46) | 708/1521 (47) | 608/1322 (46) | 0.96 |
| White | 695/1385 (50) | 747/1521 (49) | 639/1322 (48) | 0.63 |
| Other | 48/1385 (3) | 66/1521 (4) | 75/1322 (6) | 0.02 |
| Multiple birth — no./total no. (%) | 330/1391 (24) | 422/1535 (27) | 362/1348 (27) | 0.049 |
| Antenatal glucocorticoids — no./total no. (%)‡ | ||||
| Any receipt | 799/1388 (58) | 881/1532 (58) | 860/1346 (64) | <0.001 |
| Full course | 398/1386 (29) | 511/1527 (33) | 593/1342 (44) | <0.001 |
| Antenatal antibiotics — no./total no. (%)§ | 987/1388 (71) | 991/1531 (65) | 884/1345 (66) | 0.001 |
| Cesarean delivery — no./total no. (%) | 428/1388 (31) | 587/1535 (38) | 505/1345 (38) | <0.01 |
| No active treatment, according to gestational age at birth — no./total no. (%)¶ | ||||
| 22 wk | 183/241 (76) | 213/274 (78) | 186/234 (79) | 0.65 |
| 23 wk | 134/496 (27) | 150/489 (31) | 136/450 (30) | 0.39 |
| 24 wk | 40/654 (6) | 32/772 (4) | 24/664 (4) | 0.07 |
| Total | 357/1391 (26) | 395/1535 (26) | 346/1348 (26) | >0.99 |
| Surfactant treatment — no./total no. (%) | 892/1391 (64) | 1009/1533 (66) | 889/1348 (66) | 0.53 |
| Median maternal age (interquartile range) — yr | 25 (21–31) | 26 (22–31) | 27 (22–32) | <0.001 |
| Maternal education less than high school — no./total no. (%) | 235/766 (31) | 305/1023 (30) | 189/792 (24) | 0.004 |
| Infants surviving >12 hr‖ | ||||
| Total no. in cohort | 855 | 968 | 865 | |
| Severe intraventricular hemorrhage — no./total no. (%) | 236/788 (30) | 260/889 (29) | 237/824 (29) | 0.87 |
| Periventricular leukomalacia — no./total no. (%) | 58/789 (7) | 53/889 (6) | 58/822 (7) | 0.48 |
| Posthemorrhagic hydrocephalus with shunt placement — no./total no. (%) | 26/854 (3) | 10/858 (1) | 5/704 (1) | <0.001 |
| Early-onset sepsis — no./total no. (%) | 30/855 (4) | 35/967 (4) | 19/863 (2) | 0.19 |
| Late-onset sepsis — no./total no. (%) | 370/734 (50) | 447/834 (54) | 331/790 (42) | <0.001 |
| Severe retinopathy of prematurity — no./total no. (%) | 84/495 (17) | 165/535 (31) | 126/547 (23) | <0.001 |
| Necrotizing enterocolitis — no./total no. (%) | ||||
| No surgery | 41/855 (5) | 57/968 (6) | 47/864 (5) | 0.59 |
| With surgery | 66/855 (8) | 87/968 (9) | 67/864 (8) | 0.52 |
| Surgery for patent ductus arteriosus — no./total no. (%) | 163/855 (19) | 187/968 (19) | 135/862 (16) | 0.08 |
| High-frequency ventilation — no./total no. (%) | 473/855 (55) | 611/966 (63) | 547/865 (63) | <0.001 |
| Bronchopulmonary dysplasia — no./total no. (%) | 372/470 (79) | 374/511 (73) | 386/536 (72) | 0.02 |
| Postnatal glucocorticoids — no./total no. (%) | 298/853 (35) | 154/953 (16) | 169/861 (20) | <0.001 |
P values were determined using chi-square tests for categorical variables and median tests for continuous variables.
Race was determined by investigators on the basis of chart abstraction using categories specified in the study manual of operation (black, white, Asian, American Indian or Alaska Native, Native Hawaiian or other Pacific Islander, or more than one race).
Any receipt of antenatal glucocorticoids was defined as a full or partial course during the current pregnancy for the purpose of accelerating fetal maturity. A full course was defined as two doses of betamethasone (12 or 24 hours apart) or four doses of dexamethasone (≥6 hours apart).
Receipt of antenatal antibiotics was defined as receipt of any antibiotic preceding birth during the hospital admission in which delivery occurred.
Active treatment was defined as the use of surfactant, endotracheal intubation, ventilatory support (i.e., continuous positive airway pressure, bag-mask ventilation, or mechanical ventilation), chest compressions, epinephrine, or parenteral nutrition.
Data on medical conditions and therapies were available for infants surviving more than 12 hours and undergoing the applicable examination (e.g., sonogram for intraventricular hemorrhage).