Objective
We sought to determine maternal and neonatal outcomes by labor onset type and gestational age.
Study Design
We used electronic medical records data from 10 US institutions in the Consortium on Safe Labor on 115,528 deliveries from 2002 through 2008. Deliveries were divided by labor onset type (spontaneous, elective induction, indicated induction, unlabored cesarean). Neonatal and maternal outcomes were calculated by labor onset type and gestational age.
Results
Neonatal intensive care unit admissions and sepsis improved with each week of gestational age until 39 weeks ( P < .001). After adjusting for complications, elective induction of labor was associated with a lower risk of ventilator use (odds ratio [OR], 0.38; 95% confidence interval [CI], 0.28–0.53), sepsis (OR, 0.36; 95% CI, 0.26–0.49), and neonatal intensive care unit admissions (OR, 0.52; 95% CI, 0.48–0.57) compared to spontaneous labor. The relative risk of hysterectomy at term was 3.21 (95% CI, 1.08–9.54) with elective induction, 1.16 (95% CI, 0.24–5.58) with indicated induction, and 6.57 (95% CI, 1.78–24.30) with cesarean without labor compared to spontaneous labor.
Conclusion
Some neonatal outcomes improved until 39 weeks. Babies born with elective induction are associated with better neonatal outcomes compared to spontaneous labor. Elective induction may be associated with an increased hysterectomy risk.
Few issues in obstetrics and gynecology leave obstetricians more conflicted then elective induction of labor. Patients often ask for elective inductions due to logistics or discomforts. Physicians may be tempted to acquiesce for a variety of reasons. Scheduling logistics between the hospital and patient often result in deliveries occurring <39 weeks’ gestation, counter to current American College of Obstetricians and Gynecologists (ACOG) recommendations. Data suggest that inductions are contributing to the shift toward shorter gestations nationally.
For Editors’ Commentary, see Table of Contents
Over the last few years, evidence for poorer neonatal outcomes at <39 weeks has been published. In light of these data, clinicians should counsel patients on the increased risks to the neonate of a scheduled delivery <39 weeks. However, with few data available, it has been difficult to counsel patients about the maternal risks of elective induction in comparison to other labor onset types.
The studies on early term neonatal outcomes have been from single centers or used administrative data that lacked some clinical detail. Tita et al published a nationally representative multicenter study based on abstracted medical records. That study showed neonatal outcomes were worse in babies delivered <39 weeks, but it only looked at repeat cesarean deliveries.
The Consortium on Safe Labor is a National Institutes of Health multicenter collaborative study designed to characterize labor and delivery in a contemporary group of women experiencing current obstetric clinical practices. By design, study hospitals had to have obstetric electronic medical records (EMR) that coded data into prespecified fields that would allow for data to be abstracted and combined into a uniform dataset for subsequent analysis of patient-specific risk factors and maternal and neonatal outcomes. Unlike electronic administrative data, EMRs are a direct clinical source and are rich in clinical and demographic details. These data offer the advantages of a large national sample size while maintaining the clinical detail of a single-center chart review.
The current study uses a convenient cohort from the Consortium on Safe Labor database. We sought to determine neonatal and maternal outcomes by gestational age and labor onset type. While previous studies have shown that babies born <39 weeks have poorer outcomes, it is unclear whether these poorer outcomes are secondary to the reasons for delivery. It is unclear whether elective inductions in healthy women carry the same neonatal risks as indicated inductions. Previous large studies have been unable to differentiate well between causes of delivery. Furthermore, because very few data are available on maternal outcomes of elective induction in comparison to other labor onset types, we sought to explore maternal outcomes by labor onset type.
Materials and Methods
The Consortium on Safe Labor retrospectively extracted data from EMRs from 12 institutions on 228,668 deliveries with 233,844 births from 2002 through 2008. Data included demographics, prenatal complications, labor and delivery information, and maternal and neonatal outcomes. We excluded deliveries from 2 centers that did not submit indications for labor onset type (36,533), multiple gestations (8671), nonvertex deliveries (7069), gestational age <34 weeks or >42 weeks (6163), pregnancies complicated by placenta previa (205) or accreta (64), pregnancies with a prior uterine scar (cesarean or myomectomy 24,516), and fetal anomalies (8720). We removed deliveries with missing onset of labor data (25,503). There were 115,528 deliveries remaining in the dataset for analysis after exclusions.
Maternal demographics, clinical risk factors, and maternal and neonatal outcomes were categorized as discrete variables. Labor onset type was divided into 4 categories: spontaneous labor, elective induction of labor, indicated induction of labor, and unlabored cesarean delivery. These determinations were based on the listed reason for the induction or a cesarean delivery with no attempt to labor. Spontaneous labor was defined as having labored but no induction. Ultimate mode of delivery did not affect the labor onset type. If a woman had an elective induction that ended in a cesarean delivery, she was still considered an elective induction.
The neonatal outcomes that we examined were: ventilator use, asphyxia, sepsis, neonatal intensive care unit (NICU) length of stay, and NICU admissions. The maternal outcomes we examined were: chorioamnionitis, endometritis, maternal intensive care unit (ICU) admission, maternal length of stay, and hysterectomy.
We then evaluated the following demographics and risk factors: maternal age, race, ethnicity, parity, and mode of delivery for the entire sample and by labor onset type. Neonatal and maternal outcomes by labor onset type were examined. We stratified neonatal outcomes by gestational age (34–42 weeks) because of the likelihood that labor onset type might differ by gestational age and neonatal outcome is drastically different by gestational age. Differences between the groups were calculated by χ 2 and t tests where appropriate. Improvements in neonatal outcomes by week were tested with χ 2 for trend.
Multivariable logistic regression models for each of the neonatal outcomes adjusted for the following maternal complications were developed: age, parity, race/ethnicity, preeclampsia, chronic hypertension, diabetes, premature rupture of membranes, and group B streptococcus positivity (GBS+). Models for the maternal outcomes were performed adjusted for the following maternal conditions: age, parity, race/ethnicity, preeclampsia, chronic hypertension, diabetes, and GBS+.
Results
Maternal demographic characteristics are shown in Table 1 . There are significant differences in all demographics by labor onset type. NICU admission and sepsis improved for each week of gestation until 39 weeks ( Table 2 ) ( P < .01 for trend, P < .001 for 38 vs 39 weeks). Ventilator use and asphyxia improved until 38 weeks ( P = .003 for 37 vs 38 weeks). Ventilator use was different by labor onset type for all gestational ages except 41 and 42 weeks. Sepsis was statistically significantly different between labor onset types at 37-41 weeks. There were significant differences in asphyxia by labor onset types except at 37 and 40 weeks. NICU length of stay was significantly different by labor onset type at all gestational ages except 41 and 42 weeks. NICU length of stay was shortest with elective induction of labor and longest for unlabored cesarean deliveries at all gestational ages except 42 weeks, where indicated inductions had longer NICU stays than unlabored cesareans.
| Variable | Spontaneous labor, n = 77,443 | Elective induction of labor, n = 16,544 | Indicated induction of labor, n = 17,582 | Unlabored cesarean delivery, n = 3959 | P value |
|---|---|---|---|---|---|
| Age, y a | 26.8 (5.9) | 27.7 (5.3) | 27.4 (6.0) | 30.1 (6.6) | < .0001 |
| Race b | |||||
| White/non-Hispanic | 40,799 (52.7) | 12,514 (75.7) | 10,099 (57.4) | 2019 (51.0) | < .0001 |
| Black/non-Hispanic | 13,178 (17.0) | 1825 (11.0) | 3106 (17.7) | 841 (21.2) | |
| Hispanic | 15,174 (19.6) | 1243 (7.5) | 2970 (16.9) | 660 (16.7) | |
| Asian/Pacific Islander | 3770 (4.9) | 397 (2.4) | 716 (4.1) | 188 (4.8) | |
| Other race | 4522 (5.8) | 565 (3.4) | 691 (3.9) | 251 (6.3) | |
| Parity b | |||||
| 0 | 32,529 (42.0) | 4665 (28.2) | 9971 (56.7) | 2530 (63.9) | < .0001 |
| ≥1 | 44,914 (58.0) | 11,879 (71.8) | 7611 (43.3) | 1429 (36.1) |
a Continuous variables report means (SD);
| GA, wk | Type of onset | Use of ventilation | Asphyxia | ||||
|---|---|---|---|---|---|---|---|
| Frequency, n (%) | P value | Frequency, n (%) | P value | ||||
| No | Yes | No | Yes | ||||
| 34 | Spontaneous | 788 (90.4) | 84 (9.6) | .01 | 863 (99.3) | 6 (0.7) | .94 |
| Elective | 43 (93.5) | 3 (6.5) | 43 (100) | 0 (0.0) | |||
| Indicated | 175 (88.8) | 22 (11.2) | 194 (99.5) | 1 (0.5) | |||
| c/s w/o labor | 97 (80.8) | 23 (19.2) | 119 (99.2) | 1 (0.8) | |||
| 35 | Spontaneous | 1446 (94.4) | 86 (5.6) | .0004 | 1518 (99.3) | 11 (0.7) | .86 |
| Elective | 83 (97.6) | 2 (2.4) | 78 (100) | 0 (0.0) | |||
| Indicated | 311 (93.7) | 21 (6.3) | 329 (99.1) | 3 (0.9) | |||
| c/s w/o labor | 139 (86.3) | 22 (13.7) | 160 (99.4) | 1 (0.6) | |||
| 36 | Spontaneous | 3115 (96.8) | 102 (3.2) | .0007 | 3211 (99.8) | 5 (0.2) | .29 |
| Elective | 172 (98.3) | 3 (1.7) | 172 (100) | 0 (0.0) | |||
| Indicated | 813 (96.7) | 28 (3.3) | 835 (99.5) | 4 (0.5) | |||
| c/s w/o labor | 238 (92.2) | 20 (7.8) | 257 (99.6) | 1 (0.4) | |||
| 37 | Spontaneous | 7490 (99.2) | 62 (0.8) | < .0001 | 7537 (99.8) | 14 (0.2) | < .0001 |
| Elective | 581 (99.5) | 3 (0.5) | 578 (100) | 0 (0.0) | |||
| Indicated | 1817 (98.9) | 20 (1.1) | 1833 (99.9) | 2 (0.1) | |||
| c/s w/o labor | 459 (95.6) | 21 (4.4) | 471 (98.3) | 8 (1.7) | |||
| 38 | Spontaneous | 16,661 (99.7) | 42 (0.3) | .07 | 16,683 (99.9) | 19 (0.1) | .29 |
| Elective | 2502 (99.8) | 6 (0.2) | 2502 (100) | 1 (0.0) | |||
| Indicated | 3212 (99.8) | 8 (0.2) | 3219 (100) | 1 (0.0) | |||
| c/s w/o labor | 1005 (99.3) | 7 (0.7) | 1010 (99.8) | 2 (0.2) | |||
| 39 | Spontaneous | 23,650 (99.8) | 56 (0.2) | < .0001 | 23,679 (99.9) | 23 (0.1) | .38 |
| Elective | 9740 (99.9) | 14 (0.1) | 9737 (99.9) | 13 (0.1) | |||
| Indicated | 3223 (99.6) | 14 (0.4) | 3231 (99.9) | 4 (0.1) | |||
| c/s w/o labor | 1153 (98.9) | 13 (1.1) | 1163 (99.7) | 3 (0.3) | |||
| 40 | Spontaneous | 18,716 (99.8) | 45 (0.2) | .0013 | 18,739 (99.9) | 18 (0.1) | < .0001 |
| Elective | 3193 (99.7) | 11 (0.3) | 3198 (99.9) | 3 (0.1) | |||
| Indicated | 4279 (99.6) | 18 (0.4) | 4288 (99.8) | 8 (0.2) | |||
| c/s w/o labor | 555 (98.9) | 6 (1.1) | 556 (99.1) | 5 (0.9) | |||
| 41 | Spontaneous | 4675 (99.6) | 17 (0.4) | .69 | 4688 (99.9) | 4 (0.1) | .89 |
| Elective | 185 (100) | 0 (0.0) | 185 (100) | 0 (0.0) | |||
| Indicated | 3344 (99.7) | 9 (0.3) | 3349 (99.9) | 4 (0.1) | |||
| c/s w/o labor | 179 (99.4) | 1 (0.6) | 180 (100) | 0 (0.0) | |||
| 42 | Spontaneous | 404 (99.0) | 4 (1.0) | .79 | 408 (100) | ||
| Elective | 3 (100) | 0 (0.0) | 3 (100) | ||||
| Indicated | 267 (99.6) | 1 (0.4) | 268 (100) | ||||
| c/s w/o labor | 21 (100) | 0 (0.0) | 21 (100) | ||||
| Sepsis | NICU admission | ||||||
|---|---|---|---|---|---|---|---|
| Frequency, n (%) | P value | Frequency, n (%) | P value | ||||
| GA, wk | Type of onset | No | Yes | No | Yes | ||
| 34 | Spontaneous | 759 (92.1) | 65 (7.9) | .10 | 344 (39.4) | 528 (60.6) | < .0001 |
| Elective | 42 (100) | 0 (0.0) | 37 (80.4) | 9 (19.6) | |||
| Indicated | 169 (91.4) | 16 (8.6) | 73 (37.1) | 124 (62.9) | |||
| c/s w/o labor | 103 (88.0) | 14 (12.0) | 28 (23.3) | 92 (76.7) | |||
| 35 | Spontaneous | 1426 (96.4) | 53 (3.6) | .3 | 1035 (67.6) | 497 (32.4) | < .0001 |
| Elective | 78 (100) | 0 (0.0) | 71 (83.5) | 14 (16.5) | |||
| Indicated | 299 (95.8) | 13 (4.2) | 213 (64.2) | 119 (35.8) | |||
| c/s w/o labor | 144 (95.4) | 7 (4.6) | 81 (50.3) | 80 (49.7) | |||
| 36 | Spontaneous | 3130 (98.1) | 59 (1.9) | .46 | 2726 (84.7) | 491 (15.3) | < .0001 |
| Elective | 169 (98.3) | 3 (1.7) | 159 (90.9) | 16 (9.1) | |||
| Indicated | 806 (98.4) | 13 (1.6) | 678 (80.6) | 163 (19.4) | |||
| c/s w/o labor | 247 (96.9) | 8 (3.1) | 168 (65.1) | 90 (34.9) | |||
| 37 | Spontaneous | 7445 (99.0) | 73 (1.0) | < .0001 | 7050 (93.4) | 502 (6.6) | < .0001 |
| Elective | 572 (99.3) | 4 (0.7) | 548 (93.8) | 36 (6.2) | |||
| Indicated | 1814 (99.3) | 12 (0.7) | 1672 (91.0) | 165 (9.0) | |||
| c/s w/o labor | 453 (96.8) | 15 (3.2) | 381 (79.4) | 99 (20.6) | |||
| 38 | Spontaneous | 16,532 (99.4) | 107 (0.6) | .004 | 15,885 (95.1) | 818 (4.9) | < .0001 |
| Elective | 2497 (99.9) | 3 (0.1) | 2433 (97.0) | 75 (3.0) | |||
| Indicated | 3188 (99.4) | 18 (0.6) | 3022 (93.9) | 198 (6.1) | |||
| c/s w/o labor | 1003 (99.8) | 2 (0.2) | 915 (90.4) | 97 (9.6) | |||
| 39 | Spontaneous | 23,418 (99.4) | 144 (0.6) | .0002 | 22,582 (95.3) | 1124 (4.7) | < .0001 |
| Elective | 9723 (99.7) | 27 (0.3) | 9465 (97.0) | 289 (3.0) | |||
| Indicated | 3202 (99.8) | 8 (0.2) | 3040 (93.9) | 197 (6.1) | |||
| c/s w/o labor | 1150 (99.4) | 7 (0.6) | 1074 (92.1) | 92 (7.9) | |||
| 40 | Spontaneous | 18,514 (99.3) | 127 (0.7) | .0007 | 17,780 (94.8) | 981 (5.2) | < .0001 |
| Elective | 3194 (99.8) | 7 (0.2) | 3101 (96.8) | 103 (3.2) | |||
| Indicated | 4246 (99.5) | 21 (0.5) | 4067 (94.6) | 230 (5.4) | |||
| c/s w/o labor | 548 (98.6) | 8 (1.4) | 505 (90.0) | 56 (10.0) | |||
| 41 | Spontaneous | 4615 (99.3) | 34 (0.7) | .007 | 4441 (94.7) | 251 (5.3) | .0002 |
| Elective | 185 (100) | 0 (0.0) | 179 (96.8) | 6 (3.2) | |||
| Indicated | 3313 (99.3) | 23 (0.7) | 3157 (94.2) | 196 (5.8) | |||
| c/s w/o labor | 171 (97.2) | 5 (2.8) | 157 (87.2) | 23 (12.8) | |||
| 42 | Spontaneous | 401 (99.3) | 3 (0.7) | .54 | 388 (95.1) | 20 (4.9) | .09 |
| Elective | 3 (100) | 0 (0.0) | 3 (100) | 0 (0.0) | |||
| Indicated | 258 (98.1) | 5 (1.9) | 244 (91.0) | 24 (9.0) | |||
| c/s w/o labor | 21 (100) | 0 (0.0) | 18 (85.7) | 3 (14.3) | |||
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