Table 1. Maternal and Infant Characteristics and Antenatal Therapies for Infants Born at 22-28 Weeks’ Gestational Age.
| Characteristicsa | Gestational age, wk, 2013-2018 | Gestational age, wk, 2008-2012b | Adjusted difference (95% CI)c | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 22 (n = 550) | 23 (n = 1083) | 24 (n = 1398) | 25 (n = 1604) | 26 (n = 1836) | 27 (n = 1987) | 28 (n = 2419) | 22-28 (n = 10 877) | 22-28 (n = 8877) | ||
| Maternal characteristics | ||||||||||
| Age, median (IQR), y | 28 (23-32) | 28 (23-32) | 28 (24-33) | 29 (24-33) | 29 (24-33) | 29 (24-33) | 29 (24-33) | 29 (24-33) | ||
| Education, No./total (%)d | ||||||||||
| Less than high school | 61/376 (16.2) | 143/859 (16.6) | 191/1135 (16.8) | 235/1272 (18.5) | 273/1514 (18.0) | 268/1580 (17.0) | 339/1931 (17.6) | 1510/8667 (17.4) | ||
| High school diploma | 116/376 (30.9) | 238/859 (27.7) | 379/1135 (33.4) | 363/1272 (28.5) | 433/1514 (28.6) | 443/1580 (28.0) | 557/1931 (28.8) | 2529/8667 (29.2) | ||
| Trade or technical school or some college | 99/376 (26.3) | 242/859 (28.2) | 309/1135 (27.2) | 345/1272 (27.1) | 440/1514 (29.1) | 459/1580 (29.1) | 509/1931 (26.4) | 2403/8667 (27.7) | ||
| College degree or more | 100/376 (26.6) | 236/859 (27.5) | 256/1135 (22.6) | 329/1272 (25.9) | 368/1514 (24.3) | 410/1580 (25.9) | 526/1931 (27.2) | 2225/8667 (25.7) | ||
| Public medical insurancee | 312/547 (57.0) | 594/1078 (55.1) | 814/1394 (58.4) | 894/1598 (55.9) | 1064/1830 (58.1) | 1121/1978 (56.7) | 1393/2417 (57.6) | 6192/10 842 (57.1) | ||
| Hispanic or Latino ethnicity, No./total (%) | 80/544 (14.7) | 169/1070 (15.8) | 228/1390 (16.4) | 267/1585 (16.8) | 311/1821 (17.1) | 297/1971 (15.1) | 381/2395 (15.9) | 1733/10 776 (16.1) | ||
| Race, No./total (%) | ||||||||||
| American Indian or Alaska Native | 5/522 (1.0) | 6/1048 (0.6) | 14/1364 (1.0) | 12/1549 (0.8) | 21/1777 (1.2) | 30/1941 (1.5) | 37/2354 (1.6) | 125/10 555 (1.2) | ||
| Asian | 19/522 (3.6) | 39/1048 (3.7) | 50/1364 (3.7) | 59/1549 (3.8) | 66/1777 (3.7) | 92/1941 (4.7) | 113/2354 (4.8) | 438/10 555 (4.1) | ||
| Black | 251/522 (48.1) | 455/1048 (43.4) | 594/1364 (43.5) | 602/1549 (38.9) | 689/1777 (38.8) | 744/1941 (38.3) | 870/2354 (37.0) | 4205/10 555 (39.8) | ||
| Native Hawaiian or Other Pacific Islander | 7/522 (1.3) | 2/1048 (0.2) | 6/1364 (0.4) | 4/1549 (0.3) | 9/1777 (0.5) | 11/1941 (0.6) | 7/2354 (0.3) | 46/10 555 (0.4) | ||
| White | 233/522 (44.6) | 530/1048 (50.6) | 679/1364 (49.8) | 850/1549 (54.9) | 961/1777 (54.1) | 1044/1941 (53.8) | 1300/2354 (55.2) | 5597/10 555 (53.0) | ||
| >1 Race | 7/522 (1.3) | 16/1048 (1.5) | 21/1364 (1.5) | 22/1549 (1.4) | 31/1777 (1.7) | 20/1941 (1.0) | 27/2354 (1.1) | 144/10 555 (1.4) | ||
| Characteristics of pregnancy and delivery, No./total (%) | ||||||||||
| Prenatal care (≥1 visit) | 516/547 (94.3) | 1034/1081 (95.7) | 1326/1394 (95.1) | 1522/1599 (95.2) | 1759/1832 (96.0) | 1918/1984 (96.7) | 2323/2410 (96.4) | 10398/10 847 (95.9) | 8444/8834 (95.6) | 0.3 (−0.3 to 0.9) |
| Multiple gestation | 181 (32.9) | 329 (30.4) | 326 (23.3) | 369 (23.0) | 509 (27.7) | 513 (25.8) | 659 (27.2) | 2886 (26.5) | 2311 (26.0) | 0.3 (−0.9 to 1.5) |
| Chorioamnionitis documented in medical record | 127/549 (23.1) | 246/1082 (22.7) | 257/1396 (18.4) | 263/1602 (16.4) | 251/1831 (13.7) | 230/1986 (11.6) | 219/2415 (9.1) | 1593/10 861 (14.7) | ||
| Hypertension | ||||||||||
| Existing before pregnancy | 34/545 (6.2) | 104/1077 (9.7) | 177/1382 (12.8) | 227/1583 (14.3) | 266/1807 (14.7) | 344/1962 (17.5) | 351/2388 (14.7) | 1503/10 744 (14.0) | ||
| During but not before pregnancy | 15/545 (2.8) | 42/1077 (3.9) | 112/1382 (8.1) | 191/1583 (12.1) | 257/1807 (14.2) | 333/1962 (17.0) | 486/2388 (20.4) | 1436/10 744 (13.4) | ||
| Insulin-dependent diabetes | 18/542 (3.3) | 35/1077 (3.2) | 59/1385 (4.3) | 69/1588 (4.3) | 84/1818 (4.6) | 116/1964 (5.9) | 129/2388 (5.4) | 510/10 762 (4.7) | 443/8836 (5.0) | −0.1 (−0.7 to 0.5) |
| Antenatal corticosteroidsf | 177/548 (32.3) | 877/1083 (81.0) | 1266/1398 (90.6) | 1448/1601 (90.4) | 1699/1834 (92.6) | 1851/1986 (93.2) | 2253/2417 (93.2) | 9571/10 867 (88.1) | 7506/8858 (84.7) | 3.3 (2.5 to 4.2) |
| Antenatal antibiotics | 282/548 (51.5) | 808/1078 (75.0) | 1105/1394 (79.3) | 1233/1601 (77.0) | 1389/1833 (75.8) | 1517/1981 (76.6) | 1801/2412 (74.7) | 8135/10 847 (75.0) | 6249/8819 (70.9) | 4.5 (3.2 to 5.7) |
| Magnesium sulfate | 137/548 (25.0) | 761/1081 (70.4) | 1141/1396 (81.7) | 1301/1602 (81.2) | 1555/1832 (84.9) | 1697/1985 (85.5) | 2030/2414 (84.1) | 8622/10 858 (79.4) | ||
| Cesarean delivery | 17/549 (3.1) | 430/1083 (39.7) | 912/1394 (65.4) | 1096/1601 (68.5) | 1356/1836 (73.9) | 1438/1986 (72.4) | 1794/2418 (74.2) | 7043/10 867 (64.8) | 5548/8871 (62.5) | 2.4 (1.2 to 3.7) |
| Infant characteristics | ||||||||||
| Sex, No. (%) | ||||||||||
| Female | 263 (47.8) | 533 (49.2) | 671 (48.0) | 800 (49.9) | 869 (47.3) | 984 (49.5) | 1207 (49.9) | 5327 (49.0) | 4273/8873 (48.2) | |
| Male | 287 (52.2) | 550 (50.8) | 727 (52.0) | 804 (50.1) | 967 (52.7) | 1003 (50.5) | 1212 (50.1) | 5550 (51.0) | 4600/8873 (51.8) | −0.9 (−2.3 to 0.5) |
| Birth weight, median (IQR), g | 480 (431-528) | 575 (520-637) | 660 (585-730) | 760 (660-843) | 860 (745-965) | 970 (840-1090) | 1103 (950-1240) | 810 (640-1014) | ||
| Small for gestational age, No. (%)g | 38 (6.9) | 62 (5.7) | 110 (7.9) | 170 (10.6) | 184 (10.0) | 193 (9.7) | 259 (10.7) | 1016 (9.3) | 656/8873 (7.4) | 2.4 (1.6 to 3.2) |
| Major birth defect, No. (%)h | 21/550 (3.8) | 42/1083 (3.9) | 63/1396 (4.5) | 109/1603 (6.8) | 109/1835 (5.9) | 101/1985 (5.1) | 158/2416 (6.5) | 603/10 868 (5.5) | 331/8876 (3.7) | 1.8 (1.2 to 2.4) |
| Actively treated at birth, No. (%)i | 201 (36.5) | 958 (88.5) | 1369 (97.9) | 1589 (99.1) | 1827 (99.5) | 1976 (99.4) | 2400 (99.2) | 10320 (94.9) | ||
Characteristic distributions differed significantly across gestational age for maternal age, maternal race, multiple gestation, chorioamnionitis, hypertension existing before pregnancy, hypertension during but not before pregnancy, insulin-dependent diabetes, antenatal corticosteroids, antenatal antibiotics, magnesium sulfate, cesarean delivery, infant birth weight, small for gestational age, presence of birth defect, and active treatment at birth; adjusted P < .01 for all except P = .02 for insulin-dependent diabetes, adjusting for study center.
Data are from Stoll et al.1 Infants included were restricted to those with birth weights of 401 g to 1500 g, consistent with Neonatal Research Network eligibility criteria during prior years. This criterion primarily restricted eligibility for infants born at 22 weeks’ gestational age. The current cohort includes infants born at 22-28 weeks’ gestational age with any birth weight, including 163 (1.5%) with birth weights less than 401 g and 79 (0.7%) with birth weights greater than 1500 g.
Where possible given data reported by Stoll et al, differences adjusted for gestational age are shown between the proportion reported for infants born at 22-28 weeks’ gestational age in the 2013-2018 cohort vs in 2008-2012 along with associated 95% confidence intervals for the difference. A positive difference indicates that the proportion increased in the 2013-2018 cohort compared with the 2008-2012 cohort; a negative difference indicates that the proportion decreased in the 2013-2018 cohort compared with the earlier cohort.
Maternal education was assessed at the time of delivery.
Public medical insurance may include Medicaid, a state or federally funded program, or insurance obtained through the Affordable Care Act.
Antenatal corticosteroid use was defined as any antenatal corticosteroid given. Of the 9571 infants who received antenatal corticosteroids, information about whether a complete course was given was missing for 23 infants. Of the remaining 9548 infants, 7203 (75.4%) received a complete course and 2345 (24.6%) did not.
Small for gestational age was defined as less than the 10th percentile for sex and age based on Alexander percentiles.17
Major birth defect refers to any syndrome and/or major malformation including chromosomal abnormalities, central nervous system defects, congenital heart defects, gastrointestinal tract defects, genitourinary tract defects, skeletal dysplasias, cystic adenomatoid malformation, inborn errors of metabolism, and other serious or life-threatening birth defects.
Active treatment was defined as intubation, surfactant therapy, respiratory support, chest compressions, epinephrine, volume resuscitation, blood pressure support, or parenteral nutrition.22