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Trends in Postpartum Hemorrhage in the United States From 2010 to 2014

Reale, Sharon C. MD*; Easter, Sarah R. MD; Xu, Xinling PhD; Bateman, Brian T. MD, MSc*; Farber, Michaela K. MD, MS*

Author Information
doi: 10.1213/ANE.0000000000004424

Abstract

See Article, p 1303

Postpartum hemorrhage (PPH) is an important source of maternal morbidity and mortality in the United States.1–6 The prevalence of PPH increased 27.5% in the United States from 1995 to 2004 with rising rates of uterine atony as the predominant cause.1 PPH also accounted for a significant fraction of severe maternal morbidity from complications associated with hypovolemic shock and resuscitation, including coagulopathy, acute respiratory failure, and renal failure.2–5,7

Institutional, state, and national quality improvement initiatives have been implemented with the recognition that PPH is an increasing and largely preventable source of maternal morbidity and mortality. These initiatives include protocol dissemination, transfusion guideline creation, simulation development, blood loss quantification, and predelivery risk stratification.8–12 In the setting of these ongoing efforts, the aim of this study was to evaluate recent trends in PPH in the United States, including frequency, etiology, and associated maternal morbidity.

METHODS

The use of a deidentified database does not constitute human subjects research, and written informed consent was waived by the institutional review board. The data source for this study was the National Inpatient Sample (NIS), a stratified sample of discharge records designed to maximally represent all inpatient admissions in the United States.13 It is maintained by the Agency for Healthcare Research and Quality (AHRQ) as part of the Healthcare Utilization Project (HCUP). Data elements include hospital characteristics (hospital location and teaching status, hospital region, and bed size), patient demographics, and 15–30 diagnostic and procedure claims related to the inpatient hospitalization, recorded using International Classification of Disease, 9th Edition (ICD-9) codes.

A validated algorithm was used to identify hospital admissions for delivery.14 We then identified patients with a diagnosis of PPH using ICD-9 codes 666.xx.15 The etiology of PPH was defined using the following ICD-9 codes: uterine atony, 666.1x; retained placenta (including accreta), 666.0x; delayed PPH (>24 hours after delivery), 666.2x; and coagulopathy, 666.3x. Procedure codes were also used to define associated blood transfusion (99.0x) and hysterectomy (68.3x–68.9x).

Risk factors for PPH were identified from the literature16,17 and then defined using ICD-9 codes (Supplemental Digital Content, Table 1, https://links.lww.com/AA/C933). Risk factors assessed included age, delivery mode (vaginal delivery, cesarean delivery without labor, cesarean delivery with labor), previous cesarean delivery, previous uterine surgery, placenta previa, placental abruption, uterine rupture, chronic hypertension, gestational hypertension, preeclampsia, eclampsia, diabetes mellitus, polyhydramnios, chorioamnionitis, rupture of membranes >24 hours, precipitous delivery, long labor, induction of labor, macrosomia, obstructed labor, multiple gestation, grand multiparity, stillbirth, pregnancy affected by infertility, presence of uterine fibroids, race/ethnicity, and expected primary payer. The cesarean delivery with labor group was identified by women having ICD-9 codes for both cesarean delivery and labor.18

Temporal trends in the occurrence of severe maternal morbidity associated with PPH were also evaluated, including coagulopathy, hysterectomy, transfusion, acute respiratory failure, mechanical ventilation, sepsis, acute renal failure, venous thromboembolism, pulmonary embolism, maternal cardiac arrest, maternal death, discharge other than home, and length of stay >7 days.

Statistical Analysis

The NIS was redesigned in 2012, such that it became a sample of 20% of discharge records from all participating hospitals instead of a sample of 20% of all participating hospitals.13 In order for the estimates to be comparable across 5 years, appropriate trend weights provided by HCUP were used. Due to the nature of the data set, the total sample size was fixed at 37,312,324 observations.

The nationwide frequency of PPH overall and each etiology of PPH, as well as patient demographic, obstetric, and medical characteristics, were reported for each year of the study period using weighted frequencies and percentages. We first assessed for whether there was a temporal trend in the occurrence of PPH by fitting a logistic regression model with year included as the only covariate, assuming year as a continuous variable. In addition, percentage changes for the rate of PPH were calculated using a generalized linear model for binary outcome with log link function, comparing year 2010 to subsequent years, respectively.

To fully understand which factors accounted for any changes, 4 logistic models were fitted sequentially in a nested manner to determine whether secular trends in increased PPH prevalence might be explained by temporal changes in maternal demographics (model 2), delivery mode (model 3), or maternal comorbidities (model 4). All models were main effects only models, with year as a continuous variable and others as categorical variables. Odds ratios (ORs) of 1-year increase were obtained from the year variable in the models. Additional domain analysis using logistic regression models was performed to obtain the ORs of 1-year increase among patients in each hospital type and among patients with PPH. Confidence intervals (CIs) were generated using Wald confidence limits for proportions, accounting for the sample design. All analyses accounted for the survey design of the NIS and were performed in SAS software version 9.4 (SAS Institute Inc, Cary, NC) and Stata Statistical Software: Release 15 (StataCorp LLC, College Station, TX).

RESULTS

The number of delivery-related discharges from 2010 to 2014 ranged from 3,669,042 to 3,799,465. The proportion of deliveries complicated by PPH increased over time, from 2.9% in 2010 to 3.2% in 2014 (Table). The percent change in PPH rates from 2010 to 2014 was 13.0% (95% CI, 4.7%–21.9%; P = .002). Uterine atony was the leading cause of PPH, accounting for 79% of cases (Table; Supplemental Digital Content, Figure 1, https://links.lww.com/AA/C933). PPH associated with blood transfusion and hysterectomy both increased over the study period (OR, 1.04; 95% CI, 1.02–1.07; and OR, 1.03; 95% CI, 1.00–1.07, respectively) (Table). The frequencies of PPH stratified by hospital type are seen in Supplemental Digital Content, Table 2, https://links.lww.com/AA/C933.

Table. - Frequencies of PPH and Etiology According to Year of Delivery, per 1000 Deliveries
2010 2011 2012 2013 2014 Odds Ratios (95% CI)
Total deliveries 3,715,836 3,669,042 3,764,041 3,739,673 3,799,465
Postpartum hemorrhage (95% CI) 28.6 (26.7–30.6) 29.2 (26.3–32.1) 30.7 (29.6–31.8) 31.5 (30.4–32.6) 32.1 (31.0–33.3) 1.03 (1.01–1.05)
 Transfusion among deliveries 11.1 (10.2–12.0) 12.3 (11.3–13.2) 11.8 (11.3–12.3) 11.8 (11.4–12.3) 12.2 (11.7–12.8) 1.02 (0.99–1.04)
 Hysterectomy among deliveries 0.9 (0.8–0.9) 1.0 (0.9–1.1) 1.0 (0.9–1.0) 1.1 (1.0–1.1) 1.1 (1.0–1.2) 1.05 (1.02–1.09)
Causes of postpartum hemorrhage
 Uterine atony 22.3 (20.7–23.9) 22.8 (20.4–25.3) 24.3 (23.3–25.2) 25.0 (24.0–26.0) 25.8 (24.8–26.8) 1.04 (1.02–1.06)
 Retained placenta (including accreta) 2.4 (2.2–2.7) 2.5 (2.2–2.9) 2.5 (2.4–2.7) 2.6 (2.5–2.8) 2.6 (2.5–2.8) 0.99 (0.97–1.01)
 Delayed (>24 h after delivery) 2.3 (2.1–2.5) 2.4 (2.2–2.6) 2.5 (2.3–2.6) 2.5 (2.4–2.6) 2.5 (2.3–2.6) 0.99 (0.97–1.01)
 Coagulopathy 2.5 (2.0–2.9) 2.4 (2.0–2.8) 2.4 (2.2–2.5) 2.4 (2.2–2.5) 2.2 (2.0–2.3) 0.94 (0.90–0.98)
Associated morbidity
 PPH resulting in transfusion 4.0 (3.6–4.4) 4.9 (4.4–5.4) 4.7 (4.5–5.0) 4.9 (4.6–5.1) 5.0 (4.7–5.2) 1.04 (1.02–1.07)
 PPH resulting in hysterectomy 0.6 (0.5–0.7) 0.7 (0.6–0.8) 0.7 (0.6–0.8) 0.7 (0.7–0.8) 0.7 (0.6–0.8) 1.03 (1.00–1.07)
 Atony resulting in transfusion 3.0 (2.7–3.3) 3.8 (3.3–4.3) 3.7 (3.5–3.9) 3.8 (3.5–4.0) 3.9 (3.7–4.1) 1.05 (1.02–1.07)
 Atony resulting in hysterectomy 0.3 (0.3–0.3) 0.4 (0.3–0.5) 0.4 (0.3–0.4) 0.4 (0.3–0.4) 0.4 (0.3–0.4) 1.02 (0.98–1.07)
Abbreviations: CI, confidence interval; PPH, postpartum hemorrhage.

Patient characteristics that are potentially associated with PPH are shown, stratified by study year, in Supplemental Digital Content, Table 3, https://links.lww.com/AA/C933. Adjusting for changes in these characteristics did not substantially attenuate the association between study year and PPH (Figure). In the unadjusted model, the OR for PPH for each year of increase in the study period was 1.032 (95% CI, 1.012–1.052). In the fully adjusted model (model 4), the adjusted OR per year increase was 1.030 (95% CI, 1.012–1.049).

F1
Figure 1.:
The association between year and postpartum hemorrhage, sequentially adjusted for patient and hospital level risk factors. X-axis represents odds ratio and 95% confidence interval (0.99–1.06). Y-axis represents models 1–5. Model 1 = year only; Model 2 = year, age, race, primary payer; Model 3 = year, age, race, primary payer, mode of delivery (cesarean without labor, cesarean with labor); Model 4 = year, age, race, primary payer, mode of delivery (cesarean without labor, cesarean with labor), previous cesarean delivery, previous uterine surgery, previa, placental abruption, uterine rupture, chronic hypertension, gestational hypertension, preeclampsia, eclampsia, diabetes mellitus, polyhydramnios, chorioamnionitis, rupture of membranes >24 h, precipitous delivery, long labor, induction of labor, macrosomia, obstructed labor, multiple gestation, grand multiparity, still birth, pregnancy affected by infertility, and presence of uterine fibroids; and Model 5 = all factors from model 4 plus hospital location (rural, urban), hospital teaching status, hospital region (northeast, midwest, south, west), and delivery volume (first–fourth quartile).

Supplemental Digital Content, Table 4, https://links.lww.com/AA/C933, shows the sources of severe maternal morbidity in women with PPH by year. Among patients with PPH, there was a decline in the risk over time of coagulopathy (OR, 0.94; 95% CI, 0.90–0.98), acute respiratory failure (OR, 0.85; 95% CI, 0.80–0.91), and maternal death (OR, 0.83; 95% CI, 0.70–1.00), but an increase in the risk of sepsis (OR, 1.17; 95% CI, 1.08–1.28) and acute renal failure (OR, 1.10; 95% CI, 1.04–1.16).

DISCUSSION

Our analysis of recent nationwide data available in the United States suggests that the frequency of PPH has increased from 2010 and 2014, a change that was not explained by trends in the prevalence of risk factors for PPH. However, the occurrence of most measures of severe morbidity in patients with PPH has generally stabilized, and notably, the rates of coagulopathy, acute respiratory failure, and maternal death declined. This suggests that numerous quality improvement efforts at the state and national levels to attempt to decrease the risk and morbidity from PPH may be favorably impacting maternal outcomes, as reported in another recent analysis.19 However, our study has the limitations inherent in those based on NIS discharge records, including the possibility for underreporting of relevant conditions and complications.2 Identifying changes in PPH occurrence and morbidity over time will enable ongoing focus and refinement of state and national initiatives for improved PPH management.

DISCLOSURES

Name: Sharon C. Reale, MD.

Contribution: This author helped design and conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: None.

Name: Sarah R. Easter, MD.

Contribution: This author helped design and conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: None.

Name: Xinling Xu, PhD.

Contribution: This author helped conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: None.

Name: Brian T. Bateman, MD, MSc.

Contribution: This author helped design and conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: B. T. Bateman is an investigator on grants to Brigham and Women’s Hospital from the National Institutes of Health (NIH), Food and Drug Administration (FDA), Baxalta, Lilly, GlaxoSmithKline, Pfizer, and Pacira. He is a consultant to Aetion, Inc and the Alosa Foundation. He served on an expert panel for a postpartum hemorrhage quality improvement project that was conducted by the Association of Women’s Health, Obstetric and Neonatal Nurses and funded by a grant from Merck for Mothers.

Name: Michaela K. Farber, MD, MS.

Contribution: This author helped design and conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: M. K. Farber is an investigator on grants to Brigham and Women’s Hospital from Pacira and Gauss Surgical.

This manuscript was handled by: Jill M. Mhyre, MD.

FOOTNOTES

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