Abstract
Objective:
Much of the literature on clinical decision-making regarding the optimal route of delivery for periviable birth, 23 0/7 – 25 6/7 weeks’ gestation, has focused on neonatal risks. In fact, routine cesarean delivery at these early gestational ages has not been shown to improve neonatal mortality or neurological outcomes. Neonatal risks associated with route of delivery are well known. Conversely, there is a paucity of data on maternal morbidity associated with route of delivery. We examined maternal morbidity according to attempted route of delivery in women undergoing periviable birth.
Study Design:
In a secondary analysis of the Consortium on Safe Labor, a retrospective cohort study, maternal outcomes were compared between attempted vaginal delivery and planned cesarean delivery in women undergoing periviable birth. Analyses were repeated to compare maternal outcomes among actual mode of delivery (vaginal delivery vs. cesarean delivery). Multivariable Poisson regression was used to estimate adjusted relative risks (aRR) with 95% confidence intervals (95% CI), controlling for predefined covariates.
Results:
Of 678 women who underwent periviable birth, 558 (82.3%) and 120 (17.7%) attempted vaginal delivery and planned cesarean delivery, respectively. Of 558 women who attempted a vaginal delivery, 411 (73.7%) achieved a vaginal delivery. Women who attempted a vaginal delivery compared to those who had a planned cesarean delivery were less likely to have endometritis (3.1% vs. 15.0%; aRR 0.18, 95% CI 0.09-0.35). Women who attempted a vaginal delivery compared to those who had a planned cesarean delivery had 7 days shorter total length of hospital stay (P <.001). When comparing by actual mode of delivery, women with vaginal compared to cesarean delivery had decreased risks of fever (2.9% vs. 7.9%; aRR 0.42, 95% CI 0.20-0.90), endometritis (0.5% vs. 12.4%; aRR 0.03, 95% CI 0.01-0.13), and maternal thrombosis (0.2% vs. 3.0%; aRR 0.08, 95% CI 0.01-0.93). Women with vaginal delivery compared to cesarean delivery had 3 days shorter total length of hospital stay (P <.001).
Conclusion:
The majority of women (73.7%) who attempted a vaginal delivery achieved a vaginal delivery. Attempting a vaginal delivery between 23 0/7 and 25 6/7 weeks’ gestation compared to a planned cesarean delivery was associated with decreased risks of maternal infectious morbidity. Deciding the route of delivery is challenging in women undergoing periviable delivery. Our analysis provides important information on short term maternal risks when considering the risks and benefits during these discussions.
Keywords: Attempted route of delivery, Cesarean delivery, Maternal complication, Periviable delivery
Introduction:
The rate of preterm birth less than 26 weeks’ gestation was 0.4%, more than half of which were cesarean deliveries.1, 2 Improved survival in extremely preterm infants (23 0/7-27 6/7 weeks’ gestation) has led to an even higher rate of cesarean delivery in this gestational period, which is mainly indicated for malpresentation.3-6 Much of the literature on clinical decision-making regarding the optimal route of delivery has focused on neonatal risks. In fact, routine cesarean delivery for cephalic presentation at these early gestational ages has not been shown to improve neonatal mortality or neurological outcomes.7
Conversely, there is a paucity of data on maternal morbidity associated with route of delivery. Data from the Maternal-Fetal Medicine Units network published in 2015 reported that the rates of maternal complications were highest at extreme preterm (23 to 27 weeks’ gestation) compared to later gestations regardless of the mode of delivery.2 The rate of classical cesarean delivery increases steadily from 12-14% (30 0/7-31 6/7 weeks’ gestation) to 45-80% (23 0/7-27 6/7 weeks’ gestation) as gestational age decreases,6 which results in increased maternal morbidity in women delivering extremely preterm.2 In addition, women who undergo a classical cesarean delivery will subsequently require a cesarean delivery at late preterm or early term due to the risk of uterine rupture in a future pregnancy.8, 9 However, data are limited regarding whether attempting vaginal delivery in the periviable period (23 0/7 – 25 6/7 weeks’ gestation) is associated with better maternal outcomes compared with a planned cesarean delivery. The detailed information regarding maternal morbidity according to the attempted route of delivery would be useful when counseling women undergoing periviable delivery. The aim of our study was to examine maternal morbidity according to the attempted route of delivery in women undergoing preterm delivery between 23 0/7 and 25 6/7 weeks’ gestation.
Materials and Methods
This was a retrospective cohort study using data from the Consortium on Safe Labor (CSL). The CSL was a study conducted by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health and included 12 clinical centers with 19 hospitals across nine American Congress of Obstetricians and Gynecologists (ACOG) districts between 2002 and 2008 (N=228,668).10 All participating institutions obtained Institutional Review Board approval. Electronic medical record data from antenatal and labor and delivery records from each institution were collected. Neonatal intensive care unit data were also collected along with maternal and newborn discharge ICD-9 codes. Validation studies for four key outcome diagnoses found the electronic medical records were a highly accurate representation of the medical charts (> 95% for the majority of variables).10 We limited the analysis to women who delivered a singleton gestation between 23 0/7 and 25 6/7 weeks’ gestation. To prevent intraperson correlation from the same mother, only first pregnancies in the dataset were included in the analysis. We excluded women who were ineligible for vaginal delivery due to conditions such as vasa previa, placenta previa, placental abruption, fetal anomaly, human immunodeficiency virus/ herpes simplex virus, and antepartum fetal distress. We excluded pregnancies with “antepartum” fetal distress, which was different from cesarean indication “non-reassuring fetal heart tracing” because these women were less likely to have been eligible for an attempted vaginal delivery. Indications for cesarean delivery such as non-reassuring fetal heart tracing, emergency, and fetal indication can occur during labor and therefore they were retained in the analysis. Women with stillbirth were also excluded. Women with malpresentation were not excluded because the presentation would not affect maternal outcomes.
Women were classified as attempting vaginal delivery if they had at least two vaginal examinations documented in the labor progression database as previously described.10 Women were classified as undergoing planned cesarean delivery if there was only one or no cervical examination that was less than 6 cm and if there was no documentation regarding induction of labor, augmentation, spontaneous labor, failure to progress or failed induction of labor, also as previously described.10
We examined maternal demographics including maternal age, race/ethnicity, body mass index (BMI kg/m2) at delivery, parity, insurance type, diabetes (pre-existing or gestational), pregnancy-associated hypertension (gestational hypertension, preeclampsia, HELLP syndrome, superimposed preeclampsia, and eclampsia), chronic disease (chronic hypertension, asthma, thyroid disease, depression, heart, renal, or gastrointestinal disease), alcohol use, illicit drug use, smoking, previous cesarean delivery, and delivering institution. We examined the indications for delivery which included preterm premature rupture of membranes (PPROM), preterm labor, and other indicated delivery.11 Other indicated delivery included conditions such as preeclampsia, placental abruption, non-reassuring fetal heart tracing, fetal growth restriction, severe maternal medical disease, and antepartum stillbirth. The final mode of delivery was also examined.
We also examined indications for cesarean delivery including breech/malpresentation, hypertensive disease, previous uterine scar, non-reassuring fetal heart tracing, elective, chorioamnionitis, emergency, failure to progress, fetal indication, and failed induction.
Maternal outcomes as recorded in the electronic medical record and ICD-9 codes that were examined included fever, chorioamnionitis, wound separation or infection, endometritis, postpartum hemorrhage, blood transfusion, disseminated intravascular coagulation (DIC), hysterectomy, deep venous thrombosis or pulmonary embolism, and maternal death. Total length of hospital stay (days) was also examined.
Outcomes were compared between women who attempted a vaginal delivery and those who had a planned cesarean delivery. Descriptive statistics were calculated for all study variables. Chi-square test, Fisher’s exact test, Wilcoxon rank sum test, or Kruskal-Wallis tests were performed to determine associations between outcomes and attempted route of delivery. A P-value <.05 was considered significant. Multivariable Poisson regression with robust error variance was used to calculate adjusted relative risks (aRR) with 95% confidence intervals (95% CI) of each maternal outcome associated with attempting a vaginal delivery (planned cesarean delivery as referent), adjusting for maternal race, maternal age, parity, hypertension (pregnancy-associated hypertension and chronic hypertension), and delivering institution type.12 These covariates were pre-defined and selected because previous studies found these covariates were risk factors for maternal morbidity.13, 14 Analyses were repeated to compare maternal outcomes among actual mode of delivery (vaginal delivery vs. cesarean delivery). Finally, analyses were stratified by each gestational week (23, 24, and 25 weeks’ gestation). All statistical analyses were performed using SAS 9.4 (SAS Institute Inc., Cary, NC).
Results:
There were to 1374 singleton pregnancies between 23 0/7 and 25 6/7 weeks’ gestation that met the initial inclusion criteria (Figure 1). Of these, 271 (19.7%) were excluded due to placental abruption, vasa previa, and placenta previa. An additional 424 (30.9%) were excluded due to antepartum fetal distress, fetal anomaly requiring cesarean delivery, indication for cesarean delivery due to human immunodeficiency virus/herpes simplex virus, and stillbirth. Furthermore, one-woman was excluded due to having more than one pregnancy in the dataset. The final study cohort consisted of 678 women. Of 678 women, 558 (82.3%) attempted a vaginal delivery and 120 (17.7%) had a planned cesarean delivery. Of 558 women who attempted a vaginal delivery, 411 (73.7%) had a successful vaginal delivery.
Figure 1.
Cohort diagram
Abbreviations: GA (gestational age), HIV (human immunodeficiency virus)
Maternal demographics and eventual mode of delivery are presented in Table 1. Women who attempted a vaginal delivery compared to those who had a planned cesarean delivery were more likely to have pregnancy-associated hypertension, chronic hypertension, preterm labor as the precursor for delivery, and to deliver at a teaching community hospital (P<.05). Women who attempted a vaginal delivery compared to those who had a planned cesarean delivery were less likely to have prior cesarean delivery (P<.05).
Table 1.
Maternal demographics
| Attempted vaginal (n=558) | Planned cesarean (n=120) | P-value | |
|---|---|---|---|
| Maternal age, years (n=555/n=118) | .19 | ||
| < 20 | 83 (14.9) | 11 (9.3) | |
| 20-24 | 145 (26.1) | 27 (22.9) | |
| 25-29 | 135 (24.3) | 27 (22.9) | |
| 30-34 | 104 (18.7) | 26 (22.0) | |
| 35 or older | 88 (15.9) | 27 (22.9) | |
| Race/Ethnicity | .18 | ||
| Non-Hispanic white | 144 (25.8) | 25 (20.8) | |
| Non-Hispanic black | 255 (45.7) | 47 (39.2) | |
| Hispanic | 100 (17.9) | 30 (25.0) | |
| Asian or Pacific Islanders | 14 (2.5) | 4 (3.3) | |
| Other | 45 (8.1) | 14 (11.7) | |
| BMI kg/m2 at Delivery (n=393/n=96) | .27 | ||
| <25.0 | 109 (27.7) | 25 (26.0) | |
| 25.0-29.9 | 126 (32.1) | 22 (22.9) | |
| 30.0-34.9 | 73 (18.6) | 26 (27.1) | |
| 35.0-39.9 | 50 (12.7) | 14 (14.6) | |
| 40.0 or more | 35 (8.9) | 9 (9.4) | |
| Parity | .13 | ||
| 0 | 295 (52.9) | 56 (46.7) | |
| 1 | 134 (24.0) | 24 (20.0) | |
| 2 | 70 (12.5) | 23 (19.2) | |
| ≥ 3 | 59 (10.6) | 17 (14.2) | |
| Insurance | .12 | ||
| Private | 238 (42.6) | 42 (35.0) | |
| Public/Self-Pay/Other | 320 (57.4) | 78 (65.0) | |
| Pregnancy-associated hypertension | <.001 | ||
| Eclampsia | 1 (0.2) | 0 (0.0) | |
| Preeclampsia or HELLP Syndrome | 35 (6.3) | 20 (16.7) | |
| Superimposed preeclampsia | 15 (2.70) | 11 (9.2) | |
| Gestational hypertension | 4 (0.7) | 2 (1.7) | |
| Unspecified hypertension | 0 (0) | 1 (0.8) | |
| Chronic hypertension | 38 (6.8) | 27 (22.5) | <.001 |
| Chronic disease | 96 (17.2) | 23 (19.2) | .61 |
| Alcohol Use | 22 (3.9) | 1 (0.8) | .09 |
| Drug Use | 28 (5.4) | 6 (5.2) | .92 |
| Smoking | 71 (12.7) | 11 (9.2) | .28 |
| Precursor for Delivery | <.001 | ||
| PPROM | 194 (34.8) | 42 (35.0) | |
| Preterm labor | 304 (54.5) | 0 (0) | |
| Indicated delivery | 60 (10.7) | 78 (65.0) | |
| Institution type | <.001 | ||
| University-affiliated | 343 (61.5) | 101 (84.2) | |
| Teaching community hospital | 210 (37.6) | 19 (15.8) | |
| Nonteaching community hospital | 5 (0.9) | 0 (0) | |
| Mode of delivery | <.001 | ||
| Cesarean | 147 (26.3) | 120 (100) | |
| Vaginal | 411 (73.7) | 0 (0) | |
| Prior Cesarean | 62 (11.1) | 34 (28.3) | <.001 |
| Number of Prior Cesarean (n=49/n=15)a | 1 (1,2) | 1 (1,1) | .06 |
Abbreviations: BMI (body mass index); HELLP syndrome (hemolysis, elevated liver enzyme, low platelet); PPROM (preterm premature rupture of membrane)
Numbers are shown as n (%).
Significant findings are shown in bold.
Only cases with prior cesarean delivery and the number of prior cesarean deliveries are included. A median with 10%tile and 90%tile is presented. Wilcoxon rank sum test was performed for bi-variate analysis.
Indications for cesarean delivery are presented in Table 2. The most common indication for cesarean delivery was breech/malpresentation, accounting for 70% of cases. The next most common indications for cesarean delivery were hypertensive diseases, previous uterine scar and non-reassuring fetal heart rate tracing.
Table 2.
Indications for cesarean delivery
| Attempted vaginal n=147 |
Planned cesarean n=120 |
p-valuea | |
|---|---|---|---|
| Breech/Malpresentation | 101 (68.7) | 85 (70.8) | .79 |
| Hypertensive disease | 15 (10.2) | 16 (13.3) | .45 |
| Previous uterine scar | 9 (6.1) | 16 (13.3) | .06 |
| Non-reassuring fetal heart tracing | 10 (6.8) | 14 (11.7) | .20 |
| Elective | 9 (6.1) | 12 (10.0) | .26 |
| Chorioamnionitis | 10 (6.8) | 4 (3.3) | .27 |
| Emergency | 6 (4.1) | 8 (6.7) | .41 |
| Failure to progress | 13 (8.8) | 0 (0) | <.001 |
| Failed induction | 1 (0.7) | 0 (0) | >.99 |
| Fetal indication | 6 (4.1) | 5 (4.2) | >.99 |
| Other | 16 (10.9) | 16 (13.3) | .57 |
Fisher’s exact test
Significant findings are shown in bold.
Women could have more than one cesarean indications.
Maternal outcomes according to the attempted route of delivery and gestational age category are presented in Table 3. Women who attempted vaginal delivery compared to those who had a planned cesarean delivery were less likely to have endometritis (aRR 0.18, 95% CI 0.09, 0.35) and had a 7 day median shorter hospital length of stay (P<.001).
Table 3.
Maternal outcomes according to the attempted route of delivery for women delivering between 23 0/7 and 25 6/7 weeks’ gestation.
| Attempted vaginal (n=558) |
Planned cesarean (n=120) |
P-valued | Adjusted RR |
95% CI | |
|---|---|---|---|---|---|
| Fever | 22 (3.9) | 11 (9.2) | .03 | 0.46 | 0.20-1.05 |
| Chorioamnionitis | 144 (25.8) | 29 (24.2) | .82 | 0.95 | 0.68-1.34 |
| Wound Separation or Infection | 7 (1.3) | 3 (2.5) | .39 | 0.56 | 0.13-2.36 |
| Endometritis | 17 (3.1) | 18 (15.0) | <.001 | 0.18 | 0.09-0.35 |
| Hemorrhage | 29 (5.2) | 3 (2.5) | .24 | 2.21 | 0.67-7.28 |
| Transfusiona | 11 (3.4) | 2 (4.3) | .67 | 1.12 | 0.16-7.80 |
| DIC | 1 (0.2) | 1 (0.8) | .32 | 0.20 | 0.01-4.34 |
| Hysterectomy | 1 (0.2) | 1 (0.8) | .32 | 0.17 | 0.01-3.38 |
| Maternal Thrombosis/PE | 6 (1.1) | 3 (2.5) | .20 | 0.52 | 0.11-2.52 |
| Deathb | 0 (0) | 0 (0) | - | - | - |
| Hospital Length of Stay, days Median (10th, 90th)c | 4 (1,19) | 11 (3,28) | <.001e | - | - |
Abbreviation: CI (confidence interval); DIC (Disseminated intravascular coagulation); ICU (intensive care unit); PE (pulmonary embolism), RR (relative risk)
Relative risks were adjusted for maternal race, maternal age, parity, hypertension status, and hospital type.
Data presented as n(%) or median (10th, 90th percentile)
6 sites did not report the outcome
2 sites did not report the outcome; relative risk was not calculated due to few observations.
1 site did not report the outcome
Fishers exact test
Kruskal-Wallis Test
Significant findings are shown in bold.
Maternal outcomes according to the actual route of delivery and gestational age category are presented in Table 4. Women who had vaginal delivery compared to those who had a cesarean delivery were less likely to have fever (aRR 0.42, 95% CI 0.20, 0.90), endometritis (aRR 0.03, 95% CI 0.01, 0.13), or deep venous thrombosis or pulmonary embolism (aRR 0.08; 95%CI 0.01, 0.93), and had a 3 day shorter hospital length of stay (P<.001).
Table 4.
Maternal outcomes according to the actual mode of delivery
| Vaginal Delivery n=411 |
Cesarean Delivery n=267 |
P-valued | Adjusted RR | 95% CI | |
|---|---|---|---|---|---|
| Fever | 12 (2.9) | 21 (7.9) | <.001 | 0.42 | 0.20-0.90 |
| Chorioamnionitis | 107 (26.0) | 66 (24.7) | .72 | 0.88 | 0.67-1.15 |
| Wound Separation or Infection | 3 (0.7) | 7 (2.6) | .05 | 0.28 | 0.08-1.05 |
| Endometritis | 2 (0.5) | 33 (12.4) | <.001 | 0.03 | 0.01-0.13 |
| Hemorrhage | 24 (5.8) | 8 (3.0) | .10 | 1.94 | 0.91-4.11 |
| Transfusiona | 4 (1.7) | 9 (6.2) | .04 | 0.49 | 0.13-1.79 |
| DIC | 0 (0) | 2 (0.7) | .15 | - | - |
| Hysterectomy | 0 (0) | 2 (0.7) | .15 | - | - |
| Maternal Thrombosis/PE | 1 (0.2) | 8 (3.0) | <.01 | 0.08 | 0.01-0.93 |
| Deathb | 0 (0) | 0 (0) | - | - | - |
| Hospital Length of Stay, days Median (10th, 90th)c | 4 (1,19) | 7 (3,22) | <.001e | - | - |
Abbreviation: CI (confidence interval); DIC (disseminated intravascular coagulation); ICU (intensive care unit); PE (pulmonary embolism), RR (relative risk)
Relative risks were adjusted for maternal race, maternal age, parity, hypertension status, and hospital type.
6 sites did not report the outcome
2 sites did not report the outcome
1 site did not report the outcome; relative risk was not calculated due to few observations.
Fishers exact test
Kruskal-Wallis Test
Significant findings are shown in bold.
Maternal outcomes according to each gestational week are presented in Table S1-6. There were 205, 240, and 233 women who delivered at 23, 24, and 25 weeks’ gestation, respectively. Even after stratifying by gestational week, we found that attempting a vaginal delivery compared to undergoing a planned cesarean delivery was associated in general with lower risks of infectious morbidity and shorter length of hospital stay.
Discussion:
In a large multicenter cohort of women who delivered between 23 0/7 and 25 6/7 weeks’ gestation, we found that 74% of women attempting a vaginal delivery had successful vaginal deliveries. Further, attempting a vaginal delivery in this gestational age group was associated with decreased risks of infectious morbidity and shorter hospital stay. In general, the results for the analyses stratified by 23, 24 and 25 weeks of gestation were similar to the main analysis indicating that maternal benefits and risks of attempting vaginal delivery were similar across the periviable period.
We sought to evaluate maternal outcomes related to route of delivery at a periviable gestation since the focus of the majority of published literature has been on neonatal outcomes. Previous studies of preterm delivery found no differences in neonatal outcomes between attempting a vaginal delivery and a planned cesarean delivery with a fetal cephalic presentation.15-18 For pregnancies with breech presentation anticipating delivery at periviable gestation (23 0/7-24 6/7), Edmonds et al demonstrated that delivery by cesarean did not confer greater neonatal survival at 6 months though short term survival was improved.19 The executive summary of a workshop on the management of women anticipating to deliver at a periviable gestation concluded that routine cesarean delivery does not improve perinatal mortality or neurologic outcomes.7
Detailed data regarding maternal complications associated with attempted route of delivery are limited. Previous studies focused on actual mode of delivery instead of attempted mode of delivery.2, 20, 21, 22 The findings of our study which investigated maternal complications by attempted mode of delivery can provide more useful information for clinical counseling. In the cohort of 639 women who delivered between 23 0/7 and 34 0/7 weeks’ gestation, Kuper et al reported similar composite maternal outcomes in women attempting a vaginal delivery and those who had a planned cesarean delivery, though the study was underpowered to assess individual maternal outcomes.23 Further, that study was limited by a single institution and small number of patients in the earlier gestational age categories less than 26 weeks of gestation.
We found that attempting a vaginal delivery compared to a planned cesarean delivery was associated with decreased risks of fever and endometritis. These findings are not surprising since cesarean delivery is a major risk factor for surgical site infection and wound complication.24 Women attempting a vaginal delivery compared to a planned cesarean delivery also had shorter total length of hospital stay in all subgroups. Notably, women attempting a vaginal delivery compared to a planned cesarean delivery had 7 days shorter median total length of hospital stay. This finding may be due to longer postpartum stay in women who underwent cesarean delivery. It is also postulated that women who attempted a vaginal delivery were more likely to have preterm labor and therefore had shorter admission to delivery time.
A major strength of our study is the large, multicenter cohort of clinical data, which makes our findings more generalizable. Our large database enabled examination of maternal outcomes for women undergoing a periviable birth, including evaluation of unusual outcomes such as blood product transfusion, deep venous thrombosis/pulmonary embolism, or maternal ICU admission. Our findings are particularly useful since decisions regarding mode of delivery are complex and ethically challenging at a periviable gestation.25 Further, we were able to control for multiple confounders.
Our study is not without limitations. We included data of women with fetal malpresentation while acknowledging that fetal presentation is an important factor when deciding the route of delivery. Our decision to do so was based on the concepts that fetal presentation would not affect maternal outcome and that routinely performing cesarean delivery for malpresentation in the periviable period (23 0/7-25 6/7) is controversial.25 Inclusion of cases of malpresentation makes our findings applicable for women delivering in the periviable period. We classified women attempting a vaginal delivery if they had at least two vaginal examinations documented in the labor progression database. Therefore, some women in preterm labor could have been misclassified. However, this definition of labor has been consistently used in the previous CSL studies.10, 26, 27 An additional limitation is the lack of information regarding the type of uterine incision. It is known that classical hysterotomy is associated with higher risks of maternal complications compared to low transverse hysterotomy.2, 6 However, cesarean delivery at preterm gestation (especially less than 27 weeks’ gestation) compared to cesarean at term has been found to be associated with uterine rupture in a subsequent pregnancy even after a low transverse uterine incision.28, 29
In summary, we found that attempting a vaginal delivery compared to undergoing a planned cesarean delivery between 23 0/7 and 25 6/7 weeks’ gestation was associated with lower risks of infectious morbidity (such as fever and endometritis) and shorter length of hospital stay, but increased risk of maternal ICU admission. Deciding the route of delivery is challenging in women undergoing periviable delivery. Since definitive evidence for routine cesarean delivery to improve short term neonatal outcomes is lacking, the executive summary on periviable birth recommended a team approach to counseling.7 Our analysis provides important information on short term maternal risks when considering the risks and benefits during these discussions. Future studies investigating long term maternal risks including outcomes in subsequent pregnancies are needed.
Supplementary Material
Acknowledgment:
Institutions involved in the consortium, in alphabetical order: Baystate Medical Center, Springfield, MA; Cedars-Sinai Medical Center Burnes Allen Research Center, Los Angeles, CA; Christiana Care Health System, Newark, DE; EMMES Corporation (data-coordinating center), Rockville, MD; Georgetown University Hospital, MedStar Health, Washington, DC; Indiana University Clarian Health, Indianapolis, IN; Intermountain
Healthcare and University of Utah, Salt Lake City, UT; Maimonides Medical Center, Brooklyn, NY; MetroHealth Medical Center, Cleveland, OH; Summa Health System, Akron City Hospital, Akron, OH; University of Illinois at Chicago, Chicago, IL; University of Miami, Miami, FL; and University of Texas Health Science Center at Houston, Houston, TX.
Funding:
The data included in this paper were obtained from the Consortium on Safe Labor, which was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, through Contract No. HHSN267200603425C.
Research reported in this publication was supported by the National Center For Advancing Translational Sciences of the National Institutes of Health under Award Number UL1TR001409. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Footnotes
Conflict of interest:
The authors report no conflict of interest.
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