Background
Eliminating persistent racial/ethnic disparities in maternal mortality and morbidity is a public health priority. National strategies to improve maternal outcomes are increasingly focused on quality improvement collaboratives. However, the effectiveness of quality collaboratives for reducing racial disparities in maternity care is understudied.
Objective
To evaluate the impact of a hemorrhage quality-improvement collaborative on racial disparities in severe maternal morbidity from hemorrhage.
Study Design
We conducted a cross-sectional study from 2011 to 2016 among 99 hospitals that participated in a hemorrhage quality improvement collaborative in California. The focus of the quality collaborative was to implement the national maternal hemorrhage safety bundle consisting of 17 evidence-based recommendations for practice and care processes known to improve outcomes. This analysis included 54,311 women from the baseline period (January 2011 through December 2014) and 19,165 women from the postintervention period (October 2015 through December 2016) with a diagnosis of obstetric hemorrhage during delivery hospitalization. We examined whether racial/ethnic-specific severe maternal morbidity rates in these women with obstetric hemorrhage were reduced from the baseline to the postintervention period. In addition, we conducted Poisson Generalized Estimating Equation models to estimate relative risks and 95% confidence intervals for severe maternal morbidity comparing each racial/ethnic group with white.
Results
During the baseline period, the rate of severe maternal morbidity among women with hemorrhage was 22.1% (12,002/54,311) with the greatest rate observed among black women (28.6%, 973/3404), and the lowest among white women (19.8%, 3124/15,775). The overall rate fell to 18.5% (3553/19,165) in the postintervention period. Both black and white mothers benefited from the intervention, but the benefit among black women exceeded that of white women (9.0% vs 2.1% absolute rate reduction). The baseline risk of severe maternal morbidity was 1.34 times greater among black mothers compared with white mothers (relative risk, 1.34; 95% confidence interval, 1.27–1.42), and it was reduced to 1.22 (1.05–1.40) in the postintervention period. Sociodemographic and clinical factors explained a part of the black–white differences. After controlling for these factors, the black–white relative risk was 1.22 (95% confidence interval, 1.15–1.30) at baseline and narrowed to 1.07 (1.92–1.24) in the postintervention period. Results were similar when excluding severe maternal morbidity cases with transfusion alone. After accounting for maternal risk factors, the black–white relative risk for severe maternal morbidity excluding transfusion alone was reduced from a baseline of 1.33 (95% confidence interval, 1.16–1.52) to 0.99 (0.76–1.29) in the postintervention period. The most important clinical risk factor for disparate black rates for both severe maternal morbidity and severe maternal morbidity excluding transfusion alone was cesarean delivery, potentially providing another opportunity for quality improvement.
Conclusion
A large-scale quality improvement collaborative reduced rates of severe maternal morbidity due to hemorrhage in all races and reduced the performance gap between black and white women. Improving access to highly effective treatments has the potential to decrease disparities for care-sensitive acute hospital-focused morbidities.
Click Supplemental Materials under article title in Contents at ajog.org
Persistent racial/ethnic disparities in maternal mortality and morbidity exist in the United States. Black women continue to be 3–4 times more likely than white women to die during childbirth. Severe maternal morbidity (SMM) is a composite measure developed by the Centers for Disease Control and Prevention that includes diagnosis and procedure codes reflecting major complications in childbirth, such as pulmonary edema, renal failure, disseminated intravascular coagulation, hysterectomy, and transfusion. SMM is 50–100 times more common than maternal death, affecting nearly 60,000 women each year in the United States. , The risk of SMM for black women is twice that of white women, even after adjusting for sociodemographic factors and comorbidities. It is estimated that more than one half of cases of maternal mortality and morbidity are preventable and could be sensitive to quality of care provided at delivery. , Hemorrhage is the most common major complication of childbirth, the most preventable cause of maternal mortality, and by far the most frequent cause of SMM.
Why was the study conducted?
It was not known whether a large-scale quality improvement collaborative could reduce racial disparity in severe maternal complications following obstetric hemorrhage.
Key Findings
In this cross-sectional study that included 73,476 women with obstetric hemorrhage from 99 hospitals who participated in a hemorrhage quality improvement collaborative, the rate of severe maternal morbidity was reduced for all races. The black–white differences were no longer significant following case mix adjustment.
What does this add to what is known?
Maternal quality-improvement activities that focus on improving access to highly effective treatments have the potential to reduce racial disparities for care-sensitive acute hospital-focused morbidities such as hemorrhage.
Quality-improvement (QI) interventions may reduce disparities only if they improve quality of care and simultaneously reduce the performance gap between racial/ethnic groups. Disparity reduction requires that vulnerable groups with a history of worse outcomes either receive a greater degree of benefit from the quality intervention or have greater access to the intervention. Otherwise, improvement efforts may compound existing disparities by preferentially advantaging white populations. Unfortunately, little is known about the impact of QI interventions on racial disparities in maternal outcomes.
Our previous work demonstrated that a large-scale QI collaborative resulted in a significant reduction (>20%) in hemorrhage-related SMM following the implementation of a national hemorrhage safety bundle, whereas a comparison set of hospitals, not implementing the hemorrhage safety bundle, remained unchanged. In this report, we examine whether the QI collaborative would be able to reduce the gap between black and white rates of SMM from hemorrhage.
Materials and Methods
A multihospital quality collaborative focused on improving outcomes from obstetric hemorrhage was offered to all California hosptials. Ninety-nine hospitals averaging 250,000 annual births choose to participate. The collaborative, led by the California Maternal Quality Care Collaborative (CMQCC), began in January 2015 with intensive activities lasting for 18 months. This report includes 6 additional months of collaborative data not presented in an earlier report and an analysis of results by race and ethnicity.
The emphasis of the quality collaborative was to implement the national maternal hemorrhage safety bundle consisting of 17 evidence-based recommendations for practice and care processes known to improve outcomes ( Table 1 ). The implementation strategy was an adaptation of the Institute for Health Care Improvement collaborative model creating a community of learning, including 2 participant face-to-face meetings, and monthly check-in calls. Hospitals were organized into small teams of 6–8 hospitals led by physician and nurse mentors who provided QI coaching. This involved monthly team support and advice for the assessment of barriers and improvement strategies. Baseline outcome data were collected for 48 months from January 2011 through December 2014. The postintervention period was from October 2015 to December 2016. We compared baseline outcome measures with those collected in the postintervention period to examine the effect of the intervention on SMM among the racial/ethnic groups.
| Readiness domain |
| Hemorrhage cart/including instructions cards for intrauterine balloons and compression stitches |
| Immediate access to hemorrhage medications (kit or equivalent) |
| Hemorrhage response team established (anesthesia, blood bank, advanced gynecological surgery, and other services) |
| Massive transfusion protocol established |
| Emergency release protocol established for O-negative and uncross-matched units of red blood cells |
| Protocol established for those who refuse blood products |
| Unit education to hemorrhage protocols |
| Regular unit-based drills with debriefs for obstetric hemorrhage |
| Recognition and prevention domain |
| Assessment of hemorrhage risk (prenatal, admission, and other) |
| Measurement of cumulative blood loss (formal and as quantitative as possible) |
| Active management of third stage of labor (standard protocol for oxytocin at birth) |
| Response domain |
| Use of unit-standard, stage-based obstetric hemorrhage emergency management plan with checklists |
| Support program for patients, families, and staff for all major obstetric hemorrhages |
| Reporting and systems learning domain |
| Establish culture of huddles to plan for high-risk patients |
| Post-event debriefing to quickly assess what went well and what could have been improved |
| Multidisciplinary reviews of all serious hemorrhages for system issues |
| Monitor outcomes and progress in process measures in perinatal quality improvement committee |
a Based on the Alliance for Innovation in Maternal Health (AIM): Consensus Bundle on Obstetric Hemorrhage and condensed from a previous report.
There were 977,968 deliveries in the 4-year baseline period and 314,750 deliveries in the postintervention period, representing one half of all births in California. Obstetric hemorrhage was identified in approximately 6% of women in both time periods (56,865 at baseline and 20,278 during the postintervention period). Obstetric hemorrhage was defined as patients with International Statistical Classification of Diseases, Ninth and Tenth Revision diagnosis codes for antepartum or postpartum hemorrhage, placenta previa, and abruption placentae. Hemorrhage often is undercoded, which can be largely corrected by the addition of procedure codes for transfusion, given the very low rate of transfusion for other indications (codes are provided in Supplemental Table 1 ).
Discharge diagnosis and procedure codes were obtained from the CMQCC California Maternal Data Center. CMQCC uses a modified form of a previously published probabilistic algorithm to link maternal and newborn hospital discharge records with birth certificates. Linkage rates routinely exceed 98%. The baseline hemorrhage population (56,865) in this study was slightly lower than reported in the initial study (57,320) after excluding 455 (0.8%) because of nonlinkage to birth certificates resulting in missing sociodemographic factors. Birth certificates were received from the California Department of Public Health 45 days after the end of each month. Discharge files were received from the Office of Statewide Health Planning and Development on a semiannual basis (delayed by 6–9 months). Institutional review board approval was obtained from Stanford University as the study host and the California Committee for the Protection of Human Subjects for the use of the state data sets.
Self-reported race and ethnicity were obtained from birth certificates. All women were categorized into 1 of 3 ethnic groups (Hispanic, non-Hispanic, and unknown/missing), and 1 of 7 racial groups (white, black, Asian, Pacific Islander, American Indian, other, and unknown). We collapsed the “Pacific Islander” and “American Indian” groups with the “other” category and created a 5-category race/ethnicity measure: Hispanic, non-Hispanic white (white), non-Hispanic black (black), Asian, and others. In total, 4.8% of women had an unknown or missing race or ethnicity and were removed from the analysis. The final sample for analysis consisted of 54,311 women in the baseline and 19,165 women in the postintervention period.
The main outcome measure was the rate of SMM among women diagnosed with hemorrhage. Corresponding International Statistical Classification of Diseases codes for SMM are listed on the Centers for Disease Control and Prevention website. Transfusion is the most common morbidity for SMM. To identify the effect on other morbidities, we also evaluated rates of SMM excluding transfusion-only cases. As transfusion is also part of the definition for hemorrhage (widely used in all state collaboratives in the AIM project and in the prior report), the addition of SMM without transfusion in the numerator provides additional perspective.
We considered the following risk factors for SMM from obstetric hemorrhage: mother’s sociodemographic characteristics (maternal age, education, parity, and insurance status), clinical factors (number of prenatal visits, prepregnancy body mass index, multiple pregnancy, chronic hypertension, gestational diabetes, previous cesarean delivery, labor induction, preterm birth), and method of delivery. All of these factors may contribute to racial inequalities in SMM among women with obstetric hemorrhage.
Statistical analysis
We used the χ 2 test to examine whether the distributions of maternal social demographic and clinical factors are different between race/ethnic groups and whether they are different in maternal cohorts in the baseline and postintervention period. We then assessed the risk of SMM among women with obstetric hemorrhage by study period and by race/ethnicity. Specifically, we constructed Poisson generalized estimating equation models with sandwich error estimation to estimate relative risks (RRs) and 95% confidence intervals (CIs) for SMM. A estimating equation is a population-average model that accounts for within-hospital nonindependence of observations. We calculated relative risk for SMM by race/ethnicity using white women as the reference, within each study period.
We constructed an initial unadjusted model and a series of adjusted models. The initial unadjusted model included study period (baseline vs postintervention), race/ethnicity, and their interaction term. We then developed risk-adjusted models by adding maternal sociodemographic and clinical factors. We first adjusted for each covariate separately and compared the effect estimates between the unadjusted model and the single-covariate adjusted model. We then constructed a fully adjusted model by adding all covariates in the following sequence: (1) sociodemographic factors, (2) clinical factors except for the method of delivery, and (3) method of delivery. We added method of delivery separately from the other clinical factors to the model because all the other characteristics could also affect the delivery method and thus further influence SMM. Lastly, we performed sensitivity analysis by excluding each covariate one at a time from the fully adjusted model and evaluated the changes of the effect estimates. These analytical models were applied for both SMM and SMM excluding transfusion-only cases. All statistical analyses were performed using SAS 9.4 (SAS Institute Inc, Cary, NC).
Results
Participating hospitals were diverse in size, ownership, neonatal intensive care level, the volume of deliveries, patient payer mix, and geography and were representative of the state as a whole ( Table 2 ). Among the 54,311 women with obstetric hemorrhage at baseline, 42% were Hispanic, 29% were white, 15% were Asian, 5% were black, and 7% were other race/ethnicity. Racial/ethnic distribution in the postintervention period was similar to the baseline period. Maternal sociodemographic and clinical factors distributed differently across racial/ethnic groups ( Table 3 ).
| Collaborative participants | All California | |
|---|---|---|
| n (%) | n (%) | |
| Patient characteristics | ||
| Number of deliveries | 977,968 | 1,888,173 |
| Race/ethnicity | ||
| White | 309,837 (32.7) | 539,396 (29.2) |
| Black | 55,548 (5.9) | 106,530 (5.8) |
| Asian | 129,833 (13.7) | 216,504 (11.7) |
| Hispanic | 406,626 (42.9) | 912,675 (49.3) |
| Other | 45,142 (4.8) | 74,678 (4.0) |
| Missing | 30,982 | 38,390 |
| Age at delivery, y | ||
| <18 | 15,384 (1.6) | 37,752 (2.0) |
| 18–25 | 246,082 (25.2) | 547,769 (29.0) |
| 26–35 | 554,126 (56.7) | 1018273 (53.9) |
| ≥36 | 162,376 (16.6) | 284,379 (15.1) |
| Education | ||
| Some high school or less | 133,389 (14.4) | 356,203 (19.6) |
| High school/GED | 206,235 (22.3) | 461,488 (25.5) |
| Some college | 262,083 (28.4) | 477,368 (26.3) |
| College grad or more | 322,211 (34.9) | 518,204 (28.6) |
| Missing | 54,050 | 74,910 |
| Insurance | ||
| Medicaid/other government-sponsored | 364,071 (37.2) | 913,050 (48.4) |
| Private insurance | 584,349 (59.8) | 916,782 (48.6) |
| Self-pay/no insurance | 29,526 (3.0) | 58,310 (3.1) |
| Missing | 22 | 31 |
| Nulliparous | 410,607 (42.0) | 752,589 (39.9) |
| Prepregnancy BMI | ||
| <18.5 | 19,265 (2.1) | 38,587 (2.2) |
| 18.5–25 | 410,011 (44.9) | 767,776 (42.8) |
| 25–30 | 254,980 (27.9) | 512,402 (28.6) |
| 30–35 | 130,985 (14.3) | 271,290 (15.1) |
| 35–40 | 58,705 (6.4) | 121,518 (6.8) |
| ≥40 | 39,347 (4.3) | 80,951 (4.5) |
| Missing | 64,675 | 95,649 |
| Prenatal care | ||
| First trimester | 825,239 (86.0) | 1548609 (83.6) |
| Second trimester | 106,875 (11.1) | 239,552 (12.9) |
| Third trimester | 23,143 (2.4) | 54,128 (2.9) |
| No care | 4,202 (0.4) | 9,912 (0.5) |
| Missing | 18,509 | 35,972 |
| Chronic hypertension | 17,012 (1.7) | 31,024 (1.6) |
| Diabetes/gestational diabetes | 106,227 (10.9) | 187,960 (10.0) |
| Multiple gestation | 17,946 (1.8) | 31,058 (1.6) |
| Labor induction | 150,786 (15.4) | 286,710 (15.2) |
| Preterm birth (<37 wk gestation) | 76,153 (7.8) | 144,972 (7.7) |
| Previous cesarean delivery | 165,297 (16.9) | 331,037 (17.5) |
| Method of delivery: cesarean | 316,141 (32.3) | 622,465 (33.0) |
| Hospital characteristics | ||
| Number of hospitals | 99 | 238 |
| Teaching hospitals | 15 (15.2) | 30 (12.6) |
| AAP neonatal level of care | ||
| Level I | 18 (18.2) | 72 (30.3) |
| Level II | 29 (29.3) | 57 (23.9) |
| Level III | 42 (42.4) | 92 (38.7) |
| Level IV | 10 (10.1) | 17 (7.1) |
| Geographic region | ||
| Central-South Coast | 42 (42.4) | 92 (38.7) |
| Central-North Coast and Northeastern | 44 (44.4) | 96 (40.3) |
| Central Valley, Southern Inland | 13 (13.1) | 50 (21.0) |
| Rural or urban-suburban | ||
| Urban-Suburban | 94 (94.9) | 205 (86.1) |
| Rural | 5 (5.1) | 33 (13.9) |
| Average annual delivery volume (live births) | ||
| <1000 | 15 (15.2) | 72 (30.3) |
| 1000–2499 | 55 (55.6) | 117 (49.2) |
| ≥3000 | 29 (29.3) | 49 (20.6) |
| Hospital ownership | ||
| University, city, county | 11 (11.1) | 39 (16.4) |
| Integrated health system | 29 (29.3) | 29 (12.2) |
| Private nonprofit | 48 (48.5) | 128 (53.8) |
| Private investor | 11 (11.1) | 42 (17.6) |
Study period | Race/ethnicity | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| All women | White | Black | Asian | Hispanic | Other | |||||||
| Baseline | Postintervention | Baseline | Postintervention | Baseline | Postintervention | Baseline | Postintervention | Baseline | Postintervention | Baseline | Postintervention | |
| Number of women with hemorrhage | 54,311 | 19,165 | 15,775 | 5401 | 3404 | 1114 | 8180 | 3195 | 23,051 | 8161 | 3901 | 1294 |
| Characteristics | n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | n (%) |
| Age at delivery, y | ||||||||||||
| <18 | 906 (1.7) | 200 (1.0) | 76 (0.5) | 15 (0.3) | 91 (2.7) | 14 (1.3) | 13 (0.2) | 4 (0.1) | 702 (3.0) | 164 (2.0) | 24 (0.6) | 3 (0.2) |
| 18–25 | 12,774 (23.5) | 3958 (20.7) | 2700 (17.1) | 707 (13.1) | 1156 (34.0) | 320 (28.7) | 613 (7.5) | 171 (5.4) | 7737 (33.6) | 2579 (31.6) | 568 (14.6) | 181 (14.0) |
| 26–35 | 30,259 (55.7) | 11,001 (57.4) | 9674 (61.3) | 3454 (64.0) | 1622 (47.6) | 557 (50.0) | 5244 (64.1) | 2085 (65.3) | 11,391 (49.4) | 4143 (50.8) | 2328 (59.7) | 762 (58.9) |
| ≥36 | 10,372 (19.1) | 4006 (20.9) | 3325 (21.1) | 1225 (22.7) | 535 (15.7) | 223 (20.0) | 2310 (28.2) | 935 (29.3) | 3221 (14.0) | 1275 (15.6) | 981 (25.1) | 348 (26.9) |
| Education | ||||||||||||
| Some high school or less | 7486 (14.2) | 2005 (10.8) | 582 (3.8) | 132 (2.5) | 326 (10.0) | 85 (8.0) | 239 (3.0) | 79 (2.6) | 6203 (27.7) | 1682 (21.4) | 136 (3.6) | 27 (2.1) |
| High school/GED | 11,484 (21.8) | 3956 (21.3) | 2433 (15.8) | 749 (14.3) | 954 (29.1) | 296 (27.8) | 849 (10.8) | 306 (9.9) | 6732 (30.1) | 2414 (30.7) | 516 (13.6) | 191 (15.2) |
| Some college | 14,399 (27.3) | 5123 (27.6) | 4181 (27.2) | 1341 (25.5) | 1306 (39.9) | 415 (39.0) | 1399 (17.8) | 489 (15.9) | 6208 (27.7) | 2443 (31.0) | 1305 (34.5) | 435 (34.5) |
| College grad or more | 19,353 (36.7) | 7446 (40.2) | 8194 (53.2) | 3027 (57.7) | 687 (21.0) | 269 (25.3) | 5389 (68.4) | 2211 (71.7) | 3252 (14.5) | 1332 (16.9) | 1831 (48.3) | 607 (48.2) |
| Missing | 1589 | 635 | 385 | 152 | 131 | 49 | 304 | 110 | 656 | 290 | 113 | 34 |
| Insurance | ||||||||||||
| Medi-Cal/other government-sponsored | 18,697 (34.4) | 6670 (34.8) | 3079 (19.5) | 1046 (19.4) | 174 (49.2) | 573 (51.4) | 1246 (15.2) | 532 (16.7) | 11,949 (51.8) | 4229 (51.8) | 749 (19.2) | 290 (22.4) |
| Private insurance | 34,310 (63.2) | 11,987 (62.5) | 12,544 (79.5) | 4301 (79.6) | 1,673 (49.1) | 528 (47.4) | 6355 (77.7) | 2376 (74.4) | 10,630 (46.1) | 3790 (46.4) | 3108 (79.7) | 992 (76.7) |
| Self-pay/no insurance | 1303 (2.4) | 508 (2.7) | 151 (1.0) | 54 (1.0) | 57 (1.7) | 13 (1.2) | 579 (7.1) | 287 (9.0) | 472 (2.0) | 142 (1.7) | 44 (1.1) | 12 (0.9) |
| Missing | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Parity | ||||||||||||
| Multiparous | 28,613 (52.7) | 10,101 (52.7) | 7260 (46.0) | 2523 (46.7) | 1972 (57.9) | 668 (60.0) | 3725 (45.5) | 1498 (46.9) | 13,470 (58.4) | 4711 (57.7) | 2186 (56.0) | 701 (54.2) |
| Nulliparous | 25,698 (47.3) | 9064 (47.3) | 8515 (54.0) | 2878 (53.3) | 1432 (42.1) | 446 (40.0) | 4455 (54.5) | 1697 (53.1) | 9581 (41.6) | 3450 (42.3) | 1715 (44.0) | 593 (45.8) |
| Prepregnancy BMI | ||||||||||||
| <18.5 | 1079 (2.1) | 372 (2.0) | 297 (2.0) | 93 (1.8) | 73 (2.3) | 18 (1.7) | 356 (4.8) | 156 (5.1) | 286 (1.3) | 88 (1.1) | 67 (1.9) | 17 (1.4) |
| 18.5–25 | 22,140 (43.8) | 7597 (41.1) | 7692 (51.7) | 2570 (48.9) | 1015 (32.4) | 334 (31.0) | 4722 (64.3) | 1919 (62.6) | 7051 (32.7) | 2287 (29.1) | 1660 (45.9) | 487 (39.1) |
| 25–30 | 14,347 (28.4) | 5336 (28.9) | 3837 (25.8) | 1442 (27.5) | 887 (28.3) | 295 (27.3) | 1636 (22.3) | 703 (22.9) | 6919 (32.1) | 2500 (31.9) | 1068 (29.5) | 396 (31.8) |
| 30–35 | 7485 (14.8) | 2953 (16.0) | 1689 (11.4) | 660 (12.6) | 573 (18.3) | 190 (17.6) | 477 (6.5) | 218 (7.1) | 4267 (19.8) | 1691 (21.5) | 479 (13.2) | 194 (15.6) |
| 35–40 | 3287 (6.5) | 1317 (7.1) | 791 (5.3) | 283 (5.4) | 290 (9.3) | 125 (11.6) | 116 (1.6) | 55 (1.8) | 1872 (8.7) | 764 (9.7) | 218 (6.0) | 90 (7.2) |
| ≥40 | 2202 (4.4) | 914 (4.9) | 559 (3.8) | 205 (3.9) | 297 (9.5) | 117 (10.8) | 38 (0.5) | 13 (0.4) | 1182 (5.5) | 517 (6.6) | 126 (3.5) | 62 (5.0) |
| Missing | 3,771 | 676 | 910 | 148 | 269 | 35 | 835 | 131 | 1,474 | 314 | 283 | 48 |
| Prenatal care | ||||||||||||
| First trimester | 45,997 (86.2) | 16,391 (86.9) | 13,854 (89.5) | 4778 (89.9) | 2733 (82.6) | 923 (85.1) | 7245 (90.7) | 2839 (90.0) | 18,871 (83.1) | 6728 (83.7) | 3294 (85.3) | 1123 (87.7) |
| Second trimester | 5781 (10.8) | 1902 (10.1) | 1262 (8.2) | 407 (7.7) | 422 (12.8) | 123 (11.3) | 622 (7.8) | 254 (8.0) | 3022 (13.3) | 994 (12.4) | 453 (11.7) | 124 (9.7) |
| Third trimester | 1192 (2.2) | 435 (2.3) | 249 (1.6) | 91 (1.7) | 103 (3.1) | 30 (2.8) | 105 (1.3) | 61 (1.9) | 642 (2.8) | 233 (2.9) | 93 (2.4) | 20 (1.6) |
| No care | 381 (0.7) | 143 (0.8) | 114 (0.7) | 37 (0.7) | 50 (1.5) | 9 (0.8) | 18 (0.2) | 2 (0.1) | 176 (0.8) | 82 (1.0) | 23 (0.6) | 13 (1.0) |
| Missing | 960 | 294 | 296 | 88 | 96 | 29 | 190 | 39 | 340 | 124 | 38 | 14 |
| Chronic hypertension | ||||||||||||
| No | 52,981 (97.6) | 18,389 (96.0) | 15,424 (97.8) | 5215 (96.6) | 3218 (94.5) | 1025 (92.0) | 8046 (98.4) | 3118 (97.6) | 22,555 (97.8) | 7845 (96.1) | 3738 (95.8) | 1186 (91.7) |
| Yes | 1330 (2.4) | 776 (4.0) | 351 (2.2) | 186 (3.4) | 186 (5.5) | 89 (8.0) | 134 (1.6) | 77 (2.4) | 496 (2.2) | 316 (3.9) | 163 (4.2) | 108 (8.3) |
| Gestational diabetes | ||||||||||||
| No | 47,210 (86.9) | 16,511 (86.2) | 14,449 (91.6) | 4928 (91.2) | 3047 (89.5) | 985 (88.4) | 6802 (83.2) | 2626 (82.2) | 19,885 (86.3) | 6962 (85.3) | 3027 (77.6) | 1010 (78.1) |
| Yes | 7101 (13.1) | 2654 (13.8) | 1326 (8.4) | 473 (8.8) | 357 (10.5) | 129 (11.6) | 1378 (16.8) | 569 (17.8) | 3166 (13.7) | 1199 (14.7) | 874 (22.4) | 284 (21.9) |
| Multiple gestation | ||||||||||||
| No | 51,974 (95.7) | 18,377 (95.9) | 14,847 (94.1) | 5108 (94.6) | 3246 (95.4) | 1075 (96.5) | 7798 (95.3) | 3042 (95.2) | 22,290 (96.7) | 7904 (96.9) | 3793 (97.2) | 1248 (96.4) |
| Yes | 2337 (4.3) | 788 (4.1) | 928 (5.9) | 293 (5.4) | 158 (4.6) | 39 (3.5) | 382 (4.7) | 153 (4.8) | 761 (3.3) | 257 (3.1) | 108 (2.8) | 46 (3.6) |
| Labor induction | ||||||||||||
| No | 44,015 (81.0) | 15,291 (79.8) | 12,385 (78.5) | 4184 (77.5) | 2736 (80.4) | 888 (79.7) | 6703 (81.9) | 2595 (81.2) | 19,044 (82.6) | 6559 (80.4) | 3147 (80.7) | 1065 (82.3) |
| Yes | 10,296 (19.0) | 3874 (20.2) | 3390 (21.5) | 1,217 (22.5) | 668 (19.6) | 226 (20.3) | 1477 (18.1) | 600 (18.8) | 4007 (17.4) | 1602 (19.6) | 754 (19.3) | 229 (17.7) |
| Preterm birth | ||||||||||||
| No | 44,077 (81.2) | 15,803 (82.5) | 12,855 (81.5) | 4461 (82.6) | 2509 (73.8) | 851 (76.5) | 6832 (83.6) | 2718 (85.1) | 18,709 (81.2) | 6711 (82.3) | 3172 (81.4) | 1062 (82.1) |
| Yes | 10,206 (18.8) | 3352 (17.5) | 2914 (18.5) | 937 (17.4) | 889 (26.2) | 262 (23.5) | 1344 (16.4) | 476 (14.9) | 4334 (18.8) | 1445 (17.7) | 725 (18.6) | 232 (17.9) |
| Missing | 28 | 10 | 6 | 3 | 6 | 1 | 4 | 1 | 8 | 5 | 4 | 0 |
| Previous cesarean delivery | ||||||||||||
| No | 46,179 (85.0) | 16,218 (84.6) | 13,843 (87.8) | 4705 (87.1) | 2719 (79.9) | 868 (77.9) | 7045 (86.1) | 2698 (84.4) | 19,310 (83.8) | 6854 (84.0) | 3262 (83.6) | 1093 (84.5) |
| Yes | 8132 (15.0) | 2947 (15.4) | 1932 (12.2) | 696 (12.9) | 685 (20.1) | 246 (22.1) | 1135 (13.9) | 497 (15.6) | 3741 (16.2) | 1307 (16.0) | 639 (16.4) | 201 (15.5) |
| Method of delivery | ||||||||||||
| Vaginal | 32,717 (60.2) | 11,816 (61.7) | 9798 (62.1) | 3418 (63.3) | 1729 (50.8) | 566 (50.8) | 4702 (57.5) | 1881 (58.9) | 14,191 (61.6) | 5143 (63.0) | 2297 (58.9) | 808 (62.4) |
| Cesarean | 21,594 (39.8) | 7349 (38.3) | 5977 (37.9) | 1983 (36.7) | 1675 (49.2) | 548 (49.2) | 3478 (42.5) | 1314 (41.1) | 8860 (38.4) | 3018 (37.0) | 1604 (41.1) | 486 (37.6) |
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