TABLE 1.
Characteristics of the Study Cohort
| Total (n = 14 046) | Vaginal Cohort (n = 9718) | Cesarean Cohort (n = 4328) | ||||
|---|---|---|---|---|---|---|
| No IAP (n = 6989) | GBS IAPa (n = 1919) | Other Antibiotics (n = 810) | GBS IAPa (n = 573) | Other Antibiotics (n = 3755) | ||
| Maternal age,b y, median (IQR) | 28 (23–33) | 28 (23–33) | 26 (21–31) | 27 (22–31) | 26 (21–31) | 30 (25–35) |
| Maternal race and ethnicity, n (%) | ||||||
| Black, non-Hispanic | 8101 (57.7) | 3987 (57.1) | 1297 (67.6) | 522 (64.4) | 388 (67.7) | 1907 (50.8) |
| White, non-Hispanic | 3713 (26.4) | 1807 (25.9) | 403 (21.0) | 159 (19.6) | 111 (19.4) | 1233 (32.8) |
| Asian | 1007 (7.2) | 575 (8.2) | 88 (4.6) | 65 (8.0) | 30 (5.2) | 249 (6.6) |
| Hispanic | 474 (3.4) | 238 (3.4) | 49 (2.6) | 27 (3.3) | 9 (1.6) | 151 (4.0) |
| Other or unknown | 751 (5.4) | 382 (5.5) | 82 (4.3) | 37 (4.6) | 35 (6.1) | 215 (5.7) |
| Maternal BMI,b n (%) | ||||||
| <18.5 | 23 (0.2) | 19 (0.3) | 2 (0.1) | 0 | 0 | 2 (0.1) |
| 18.5 to <25.0 | 1868 (13.3) | 1167 (16.7) | 239 (12.5) | 126 (15.6) | 40 (7.0) | 296 (7.9) |
| 25.0 to <30.0 | 4978 (35.4) | 2704 (38.8) | 631 (32.9) | 277 (34.3) | 151 (26.4) | 1215 (32.4) |
| ≥30.0 | 7148 (50.9) | 3081 (44.2) | 1045 (54.5) | 405 (50.1) | 381 (66.6) | 2236 (59.6) |
| Parity,b n (%) | ||||||
| 1 | 6377 (45.4) | 2995 (42.8) | 1060 (55.2) | 325 (40.1) | 444 (77.5) | 1553 (41.4) |
| 2 or more | 7537 (53.7) | 3916 (56.0) | 852 (44.4) | 476 (58.8) | 126 (22.0) | 2167 (57.7) |
| GBS status, n (%) | ||||||
| Negative | 9325 (66.4) | 6119 (87.6) | 62 (3.2) | 258 (31.9) | 31 (5.4) | 2855 (76.0) |
| Positive | 3927 (28.0) | 432 (6.2) | 1810 (94.3) | 528 (65.2) | 530 (92.5) | 627 (16.7) |
| Unknown | 794 (5.7) | 438 (6.3) | 47 (2.5) | 24 (3.0) | 12 (2.1) | 273 (7.3) |
| Chorioamnionitis, n (%) | 781 (5.6) | 83 (1.2) | 113 (5.9) | 215 (26.5) | 100 (17.5) | 270 (7.2) |
| Maternal asthma, n (%) | 1909 (13.6) | 901 (12.9) | 297 (15.5) | 99 (12.2) | 105 (18.3) | 507 (13.5) |
| Maternal allergy, n (%) | 923 (6.6) | 427 (6.1) | 127 (6.6) | 55 (6.8) | 43 (7.5) | 271 (7.2) |
| Proportion of residents with less than high school education,b,c median (IQR) | 0.17 (0.08–0.27) | 0.17 (0.08–0.28) | 0.18 (0.09–0.28) | 0.18 (0.09–0.28) | 0.19 (0.09–0.29) | 0.15 (0.06–0.26) |
| Median HHI quartiles,b,c $, n (%) | ||||||
| ≤27 800 | 3490 (24.9) | 1736 (24.8) | 563 (29.3) | 235 (29.0) | 162 (28.3) | 794 (21.2) |
| 27 801 to ≤39 610 | 3489 (24.8) | 1794 (25.7) | 490 (25.5) | 210 (25.9) | 150 (26.2) | 845 (22.5) |
| 39 611 to ≤62 315 | 3489 (24.8) | 1742 (24.9) | 457 (23.8) | 202 (24.9) | 142 (24.8) | 946 (25.2) |
| ≥62 316 | 3487 (24.8) | 1671 (23.9) | 395 (20.6) | 156 (19.3) | 117 (20.4) | 1148 (30.6) |
| Infant’s sex (male), n (%) | 7136 (50.8) | 3446 (49.3) | 998 (52.0) | 415 (51.2) | 260 (45.4) | 1791 (47.7) |
| Birth weight, g, median (IQR) | 3310 (3013–3613) | 3290 (3000–3575) | 3304 (3025–3600) | 3290 (3013–3580) | 3425 (3100–3745) | 3340 (3020–3680) |
| Birth weight for GA z score,d mean (SD) | −0.17 (0.86) | −0.22 (0.82) | −0.22 (0.81) | −0.23 (0.79) | −0.13 (0.92) | −0.05 (0.94) |
| Neonatal antibiotics,e n (%) | 1134 (8.1) | 315 (4.5) | 165 (8.6) | 185 (22.8) | 97 (16.9) | 372 (9.9) |
| Breastfeeding at 3 mo,b n (%) | 6077 (43.3) | 3141 (44.9) | 774 (40.3) | 328 (40.5) | 206 (36.0) | 1628 (43.3) |
| Cohort retained at >4 completed years of age,f n (%) | 10 404 (74.1) | 5133 (73.4) | 1425 (74.3) | 604 (74.6) | 414 (72.3) | 2828 (75.3) |
| Asthmag | 2208 (21.2) | 1039 (20.2) | 343 (24.1) | 127 (21.0) | 118 (28.5) | 581 (20.5) |
| Eczemag | 1331 (12.8) | 629 (12.3) | 216 (15.2) | 71 (12.0) | 74 (17.9) | 341 (12.1) |
| Food allergyg | 716 (6.9) | 326 (6.4) | 104 (7.3) | 49 (8.1) | 32 (7.7) | 205 (7.3) |
| Allergic rhinitisg | 1414 (13.6) | 657 (12.8) | 195 (13.7) | 80 (13.3) | 69 (16.7) | 413 (14.6) |
GA, gestational age; HHI, household income; IQR, interquartile range.
GBS IAP is defined as the intrapartum administration of penicillin, ampicillin, cefazolin, clindamycin, or vancomycin 4 or more hours before delivery; antibiotics not meeting the definition of GBS IAP are categorized as other antibiotics.
Missing values for each characteristic were <1% of the total cohort and, thus, are not displayed in the tables. Information is missing for the following numbers of study subjects: maternal age, 4; maternal BMI, 29; parity, 132; proportion of residents with less than high school education, 64; median household income, 91; breastfeeding at 3 mo, 10. The percent missing value is included in the denominator for total proportions; missing values are excluded in proportion for the columns stratified by delivery mode unless ≥1%.
Proportion of residents with less than high school education and median household income are derived from American Community Survey 2009 to 2012 data including American Community Survey tract-level data (detailed definition in Supplemental Table 6).
Sex-specific Birth weight for GA z scores were derived from Fenton growth charts.38
Neonatal antibiotics are defined as any intravenous or intramuscular antibiotic administered to an infant within 72 h after birth.
Includes all infants who had at least 1 pediatric visit after 4 completed years of age.
Percent displayed are percentage of cohort retained for >4 completed years of age.