Table 4.
Smaller Standardized Difference for Maternal and Neonatal Characteristics After Propensity Score Matchinga.
| Original Sample | Matched Sample | |||||
|---|---|---|---|---|---|---|
| Prolonged antibiotics n=2936 | No prolonged antibiotics n=2786 | Standardized difference | Prolonged antibiotics n=2181 | No prolonged antibiotics n=2181 | Standardized difference | |
| Maternal education | ||||||
| < High School degree | 597 (20.3) | 533 (19.1) | 0.030 | 442 (20.3) | 439 (20.1) | 0.003 |
| High School degree | 788 (26.8) | 813 (29.2) | 0.052 | 605 (27.7) | 618 (28.3) | 0.013 |
| > High School degree | 1,280 (43.6) | 1,176 (42.2) | 0.028 | 929 (42.6) | 924 (42.4) | 0.005 |
| Maternal medical insurance | ||||||
| Private | 1,174 (40.0) | 1,029 (36.9) | 0.063 | 826 (37.9) | 828 (38.0) | 0.002 |
| Maternal race/ethnicity | ||||||
| Black, non-Hispanic | 1,278 (43.5) | 1,194 (42.9) | 0.014 | 965 (44.2) | 972 (44.6) | 0.006 |
| White, non-Hispanic | 1,063 (36.2) | 1,072 (38.5) | 0.047 | 786 (36.0) | 779 (35.7) | 0.007 |
| Hispanic | 433 (14.7) | 418 (15.0) | 0.007 | 330 (15.1) | 336 (15.4) | 0.008 |
| Maternal hypertension | 591 (20.1) | 733 (26.3) | 0.147 | 501 (23.0) | 518 (23.8) | 0.019 |
| Antepartum hemorrhage | 571 (19.4) | 597 (21.4) | 0.049 | 432 (19.8) | 442 (20.3) | 0.011 |
| Maternal clinical chorioamnionitis | 719 (24.5) | 269 (9.7) | 0.402 | 323 (14.8) | 269 (12.3) | 0.067 |
| Maternal antibiotics during delivery admission | 2,243 (76.4) | 1,992 (71.5) | 0.112 | 1,606 (73.6) | 1,583 (72.6) | 0.024 |
| Antenatal steroids | 2,586 (88.1) | 2,504 (89.9) | 0.057 | 1,930 (88.5) | 1,936 (88.8) | 0.009 |
| Cesarean section | 1,764 (60.1) | 1,887 (67.7) | 0.160 | 1,370 (62.8) | 1,407 (64.5) | 0.035 |
| Membrane rupture >18 hours | 927 (31.6) | 569 (20.4) | 0.256 | 563 (25.8) | 527 (24.2) | 0.038 |
| GA week | ||||||
| 22 | 47 (1.6) | 30 (1.1) | 0.046 | 24 (1.1) | 26 (1.2) | 0.008 |
| 23 | 414 (14.1) | 226 (8.1) | 0.191 | 246 (11.3) | 216 (9.9) | 0.044 |
| 24 | 836 (28.5) | 652 (23.4) | 0.116 | 589 (27.0) | 568 (26.0) | 0.022 |
| 25 | 900 (30.7) | 923 (33.1) | 0.053 | 708 (32.5) | 706 (32.4) | 0.002 |
| BW grams, mean (SD) | 705 (137) | 735 (138) | 0.223 | 716 (137) | 721 (137) | 0.043 |
| Male | 1,509 (51.4) | 1,371 (49.2) | 0.044 | 1,118 (51.3) | 1,105 (50.7) | 0.012 |
| Endotracheal intubation at birth | 2,520 (85.8) | 2,192 (78.7) | 0.188 | 1,826 (83.7) | 1,815 (83.2) | 0.013 |
| Infant temperature within 60 minutes of birth | ||||||
| ≥ 96.5 F | 1,977 (67.3) | 1,998 (71.7) | 0.095 | 1,507 (69.1) | 1,505 (69.0) | 0.002 |
| < 96.5 F | 741 (25.2) | 612 (22.0) | 0.077 | 519 (23.8) | 528 (24.2) | 0.010 |
| Highest respiratory support at 24 hours | ||||||
| High-frequency ventilation | 689 (23.5) | 230 (8.3) | 0.426 | 317 (14.5) | 230 (10.5) | 0.112 |
| Conventional ventilation | 1,684 (57.4) | 1,652 (59.3) | 0.039 | 1,366 (62.6) | 1,402 (64.3) | 0.033 |
| NIMV | 117 (4.0) | 166 (6.0) | 0.091 | 101 (4.6) | 111 (5.1) | 0.021 |
| CPAP | 375 (12.8) | 650 (23.3) | 0.277 | 340 (15.6) | 378 (17.3) | 0.046 |
| Severe IVH diagnosed within 7 days | 252 (8.6) | 120 (4.3) | 0.175 | 142 (6.5) | 117 (5.4) | 0.047 |
| Enteral feeds started within 3 days | 773 (26.3) | 1,091 (39.2) | 0.276 | 635 (29.1) | 649 (29.8) | 0.014 |
BW, birth weight; CPAP, continuous positive airway pressure; GA, gestational age; IVH, intraventricular hemorrhage; NIMV, non-invasive intermittent mandatory ventilation; SD, standard deviation.
N (%) are shown for all variables except BW reported as mean and standard deviation. Standardized differences are shown as absolute value. The original sample includes 5722 infants with all non-missing values of the covariates included in the propensity score model from the total 5807 infants in the complete cohort. Categorical variables with missing values for ≥1% of infants were entered in the model with a level indicating missing in order to minimize the number of observations excluded due to missing values (maternal education, 10% missing; maternal medical insurance, 1%; membrane rupture >18 hours, 1%; infant temperature within 60 minutes of birth, 7%; severe IVH diagnosed with 7 days, 1%).