Table 1. Demographic and pregnancy characteristics by gestational age group of index cesarean delivery.
| Periviable (20 – 26 weeks) N=456 |
Term (37 – 41 weeks) N=10,505 |
p-value1 | |
|---|---|---|---|
| Index pregnancy | |||
| Maternal age (years) | <0.001 | ||
| Mean (SD) | 23.7 (5.8) | 25.7 (6.1) | |
| Missing: N (%) | 0 (0) | 12 (<1) | |
| Maternal race: N (%)2 | <0.001 | ||
| White | 310 (68) | 8022 (76) | |
| Non-white | 125 (27) | 1986 (19) | |
| Missing | 21 (5) | 497 (5) | |
| Gestational age (weeks) | |||
| Median (IQR) | 25 (24 – 26) | 40 (39 – 40) | – |
| Missing N (%) | 0 (0) | 0 (0) | |
| Birth weight (grams) | |||
| Mean (SD) | 756 (202) | 3589 (499) | – |
| Missing N (%) | 0 (0) | 0 (0) | |
| Incision type: N (%) | <0.001 | ||
| Low transverse | 228 (50) | 9558 (91) | |
| Classical | 163 (36) | 61 (<1) | |
| Other | 1 (<1) | 11 (<1) | |
| Missing | 64 (14) | 875 (8) | |
| Subsequent pregnancy | |||
| Maternal age (years) | <0.001 | ||
| Mean (SD) | 26.7 (6.0) | 28.9 (6.0) | |
| Missing: N (%) | 0 (0) | 2 (<1) | |
| Maternal obesity: N (%) | 0.08 | ||
| No | 253 (55) | 6152 (58) | |
| Yes | 63 (14) | 1968 (19) | |
| Missing | 140 (31) | 2385 (23) | |
| Prior live births: N (%) | <0.001 | ||
| 0 | 71 (16) | 198 (2) | |
| 1 | 225 (49) | 8552 (81) | |
| 2 | 89 (20) | 1031 (10) | |
| 3 or more | 51 (11) | 508 (5) | |
| Missing | 20 (4) | 216 (2) | |
| Inter-delivery interval (months) | 0.07 | ||
| Median (IQR) | 28 (18 – 45) | 32 (23 – 47) | |
| Missing N (%) | 0 (0) | 0 (0) | |
| Maternal smoking: N (%) | <0.001 | ||
| No | 346 (76) | 8903 (85) | |
| Yes | 91 (20) | 1316 (12) | |
| Missing | 19 (4) | 286 (3) | |
| Maternal income (× 103) | <0.001 | ||
| Median (IQR) | 37.9 (30.7 – 47.6) | 42.5 (33.5 – 54.6) | |
| Missing: N (%) | 18 (4) | 215 (2) | |
| Hypertension: N (%) | 75 (16) | 670 (6) | <0.001 |
| Diabetes: N (%) | 0.64 | ||
| No | 423 (93) | 9712 (92) | |
| Gestational | 25 (5) | 651 (6) | |
| Established | 8 (2) | 142 (1) | |
| Gestational age (weeks) | <0.001 | ||
| Median (IQR) | 37 (35 – 38) | 39 (38 – 40) | |
| Missing: N (%) | 7 (2) | 150 (1) | |
| Birth weight (grams) | <0.001 | ||
| Mean (SD) | 2763 (841) | 3509 (542) | |
| Missing: N (%) | 5 (1) | 53 (<1) | |
| Induction/augment: N (%) | <0.001 | ||
| No | 420 (92) | 8824 (84) | |
| Yes | 36 (8) | 1681 (16) | |
| Delivery mode: N (%) | 0.01 | ||
| Vaginal | 92 (20) | 2681 (26) | |
| Cesarean | 364 (80) | 7822 (74) | |
| Missing | 0 (0) | 2 (<1) |
1
Analyses exclude missing values
2
SD = Standard deviation and IQR = Interquartile range.
3
Race was categorized as white or non-white using data collected at both first and subsequent pregnancies. We assumed that a person's race did not vary over time, so that if race was missing for a subject's first pregnancy we could use a non-missing race value from the subsequent pregnancy, and vice versa.
4
Data on maternal income at the subsequent pregnancy was missing and filled in with data from the first pregnancy for 273 patients, 259 (2.5%) in the term and 14 (3.6%) in the periviability delivery group (p=0.17).