Background
Both maternal mortality rate and severe maternal morbidity rate have risen significantly in the United Sates. Recently, the Centers for Disease Control and Prevention introduced International Classification of Diseases, 9th revision, criteria for defining severe maternal morbidity with the use of administrative data sources; however, those criteria have not been validated with the use of chart reviews.
Objective
The primary aim of the current study was to validate the Centers for Disease Control and Prevention International Classification of Diseases, 9th revision, criteria for the identification of severe maternal morbidity. This analysis initially required the development of a reproducible set of clinical conditions that were judged to be consistent with severe maternal morbidity to be used as the clinical gold standard for validation. Alternative criteria for severe maternal morbidity were also examined.
Study Design
The 67,468 deliveries that occurred during a 12-month period from 16 participating California hospitals were screened initially for severe maternal morbidity with the presence of any of 4 criteria: (1) Centers for Disease Control and Prevention International Classification of Diseases, 9th revision, diagnosis and procedure codes; (2) prolonged postpartum length of stay (>3 standard deviations beyond the mean length of stay for the California population); (3) any maternal intensive care unit admissions (with the use of hospital billing sources); and (4) the administration of any blood product (with the use of transfusion service data). Complete medical records for all screen-positive cases were examined to determine whether they satisfied the criteria for the clinical gold standard (determined by 4 rounds of a modified Delphi technique). Descriptive and statistical analyses that included area under the receiver operating characteristic curve and C-statistic were performed.
Results
The Centers for Disease Control and Prevention International Classification of Diseases, 9th revision, criteria had a reasonably high sensitivity of 0.77 and a positive predictive value of 0.44 with a C-statistic of 0.87. The most important source of false-positive cases were mothers whose only criterion was 1-2 units of blood products. The Centers for Disease Control and Prevention International Classification of Diseases, 9th revision, criteria screen rate ranged from 0.51-2.45% among hospitals. True positive severe maternal morbidity ranged from 0.05-1.13%. When hospitals were grouped by their neonatal intensive care unit level of care, severe maternal morbidity rates were statistically lower at facilities with lower level neonatal intensive care units ( P < .0001).
Conclusion
The Centers for Disease Control and Prevention International Classification of Diseases, 9th revision, criteria can serve as a reasonable administrative metric for measuring severe maternal morbidity at population levels. Caution should be used with the use of these criteria for individual hospitals, because case-mix effects appear to be strong.
Over the last 15 years both maternal mortality and morbidity rates have risen significantly in the United States. Despite the increasing rate, maternal mortality remains a rare event and difficult to track in a timely manner. Depending on the definition, severe maternal morbidity occurs 50-100 times more frequently than death and identifies cases that were on a pathway to death. A measure of severe maternal morbidity based on administrative data would provide rapid assessments of maternal health at both hospital and population levels and track progress of large-scale care-improvement projects.
Kuklina et al and Geller et al established criteria for identification of “near miss” maternal morbidity at the hospital level focusing on maternal intensive care unit (ICU) admission or transfusion of ≥4 units of any blood product. These criteria were validated and proposed for national use for internal hospital quality reviews (with the slight revision of ≥4 units of red blood cells). Unfortunately, these criteria are not present in administrative data sets that would prevent their use for population-level assessments. In contrast, investigators at the Centers for Disease Control and Prevention (CDC) used a set of International Classification of Disease, 9 th Edition, Clinical Manual (ICD-9 CM) diagnosis and procedure codes that are associated with maternal death to identify potential cases of severe maternal morbidity (referred to as CDC ICD-9 criteria; Table 1 ). However, the accuracy of the CDC ICD-9 criteria in the identification of women with true severe maternal morbidity has not been evaluated with the use of actual patient records. The primary aim of the current study was to validate the CDC ICD-9 criteria in the identification of severe maternal morbidity by reviewing medical records from a large representative sample of cases picked up by the CDC ICD-9 criteria. This analysis required the development of a reproducible set of clinical conditions that were judged to be consistent with severe maternal morbidity and hence used as the clinical gold standard for determination of true severe maternal morbidity. The CDC ICD-9 criteria and “Gold Standard” rates of severe maternal morbidity were then compared among hospital levels of care. A secondary aim was to identify any ICD-9 or procedure code additions or deletions that could improve the CDC ICD-9 criteria.
| Indicator | Code |
| Acute myocardial infarction | 410.xx |
| Acute renal failure | 584.x, 669.3x |
| Adult respiratory distress syndrome | 518.5, 518.81, 518.82, 518.84,799.1 |
| Amniotic fluid embolism | 673.1x |
| Aneurysm | 441.xx |
| Cardiac arrest/ventricular fibrillation | 427.41, 427.42, 427.5 |
| Disseminated intravascular coagulation | 286.6, 286.9, 666.3x |
| Eclampsia | 642.6x |
| Heart failure during procedure or surgery | 669.4x, 997.1 |
| Internal injuries of thorax, abdomen, and pelvis | 860.xx-869.xx |
| Intracranial injuries | 800.xx, 801.xx, 803.xx, 804.xx, 851.xx-854.xx |
| Puerperal cerebrovascular disorders | 430, 431, 432.x, 433.xx, 434.xx, 436, 437.x, 671.5x, 674.0x, 997.2, 999.2 |
| Pulmonary edema | 428.1, 518.4 |
| Severe anesthesia complications | 668.0x, 668.1x, 668.2x |
| Sepsis | 038.xx, 995.91, 995.92, 670.2 b |
| Shock | 669.1x, 785.5x, 995.0, 995.4, 998.0 |
| Sickle cell anemia with crisis | 282.62, 282.64, 282.69 |
| Thrombotic embolism | 415.1x, 673.0x, 673.2x, 673.3x, 673.8x |
| International Classification of Diseases, 9th revision, Clinical Modification procedure codes | |
| Blood transfusion | 99.0x |
| Cardio monitoring | 89.6x |
| Conversion of cardiac rhythm | 99.6x |
| Hysterectomy | 68.3x-68.9 |
| Operations on heart and pericardium | 35.xx, 36.xx, 37.xx, 39.xx |
| Temporary tracheostomy | 31.1 |
| Ventilation | 93.90, 96.01-96.05, 96.7x |
a Available at: http://www.cdc.gov/reproductivehealth/MaternalInfantHealth/SevereMaternalMorbidity.html (accessed December 15, 2015)
b One additional code (670.2) has been added to the Severe Maternal Morbidity code set defined by the Centers for Disease Control and is now part of Title V grants applications (available at: http://mchb.hrsa.gov/programs/titlevgrants/fadresource.pdff . Accessed December 15 th 2015.
Methods
Our study sample included all mothers who delivered at >20 weeks of gestation from July 1, 2012, through June 30, 2013, from 16 participating hospitals that were representative of all regions of California (including urban and suburban) and all levels of neonatal intensive care. We intentionally sought a higher representation of regional perinatal centers and hospitals with a greater percentage of African American births to reflect a wide range of cases with severe maternal mortality rates. We used 4 screening strategies initially to identify cases of potential severe maternal morbidity for chart review. These included all mothers with any of the following events: (1) CDC ICD-9 diagnosis and procedure codes, (2) prolonged postpartum length of stay (PPLOS) defined as 3 standard deviations beyond the mean length of stay for the California population (4 days for a vaginal delivery; 6 days for a cesarean delivery), (3) any maternal ICU admissions, and (4) administration of any blood product. The first 2 screening criteria used data from the California Maternal Data Center that linked patient discharge diagnosis data with birth certificate data; the other screening methods (ICU and blood administration) used alternate hospital data sources (chargemaster files, admission discharge transfer files, and blood bank data systems). Only data from the birth admission were analyzed because antenatal and postpartum admissions were more difficult to identify reliably in our data sets.
The case review team was comprised of 10 obstetric researchers who were experienced in quality reviews, several of whom had specific experience in assessment of severe maternal morbidity. The team first developed a set of consensus clinical conditions to establish a “gold standard” to identify severe maternal morbidity. This process started with previously established criteria that included near miss and organ failure and expanded to severe temporary harm and additional significant procedures. We incorporated a patient-orientated view that focused on complications that have significant impact on the woman and her family. Consensus was developed with a modified Delphi method. Some clinical conditions, typically those that were “near miss,” reached immediate consensus, but others required more discussion. To build consistency among reviewers, we created a series of 30 case scenarios to explore borderline situations. After team discussion, if consensus was not reached, the investigators constructed pro and con arguments and potential principles to guide the next round of deliberations. The clinical team went through 4 rounds of the Delphi process before reaching consensus on all case scenarios and completing the final version of the Gold Standard Severe Maternal Morbidity Case Review Guidelines ( Table 2 ). During chart review, if severe maternal morbidity categorization was still not clear-cut, the case was discussed during weekly research-team phone calls, and assignment was made by consensus. At the time of chart review, investigators were blinded to the ICD-9 diagnosis codes but were provided the number of units of blood that had been transfused (derived from blood bank data), the procedures that occurred during the hospital admission, and the number of days spent in the ICU. Cases identified by these gold standard criteria are referred to as “true positives.”
| Severe maternal morbidity | NOT severe morbidity (insufficient evidence, if this is the only criteria) |
|---|---|
| Hemorrhage | |
| Obstetric hemorrhage with ≥4 units of red blood cells transfused | Obstetric hemorrhage with 2-3 units of red blood cells transfused ALONE |
| Obstetric hemorrhage with 2 units of red blood cells and 2 units of fresh frozen plasma transfused (without other procedures or complications), if not judged to be “over- exuberant” transfusion | Obstetric hemorrhage with 2 units of red blood cells and 2 units of fresh frozen plasma transfused AND judged to be “over-exuberant” |
| Obstetric hemorrhage with <4 units of blood products transfused and evidence of pulmonary congestion that requires >1 dose of Lasix | Obstetric hemorrhage with <4 units of blood products transfused and evidence of pulmonary edema requiring only 1 dose of Lasix |
| Obstetric hemorrhage with return to operating room for any major procedure (excludes dilation) | |
| Any emergency/unplanned peripartum hysterectomy, regardless of number of units transfused (includes all placenta accretas) | Planned peripartum hysterectomy for cancer/neoplasia |
| Obstetric hemorrhage with uterine artery embolization, regardless of number of units transfused | |
| Obstetric hemorrhage with uterine balloon or uterine compression suture placed and 2-3 units of blood products transfused | Obstetric hemorrhage with uterine balloon or uterine compression suture placed and ≤1 units of blood products transfused |
| Obstetric hemorrhage admitted to intensive care unit for invasive monitoring or treatment (either medication or procedure; not just observed overnight) | Any obstetric hemorrhage that went to the intensive care unit for observation only without further treatment |
| Hypertension/neurologic | |
| Eclamptic seizure(s) or epileptic seizures that were “status” | |
| Continuous infusion (intravenous drip) of an antihypertensive medication | |
| Nonresponsiveness or loss of vision, permanent or temporary (but not momentary), documented in physician’s progress notes | |
| Stroke, coma, intracranial hemorrhage | |
| Preeclampsia with difficult to control severe hypertension (>160 systolic blood pressure or >110 diastolic blood pressure) that requires multiple intravenous doses and/or persistent ≥48 hours after delivery | Chronic hypertension that drifts up to the severe range and needs postoperative medication dose alteration: preeclampsia blood pressure control with oral medications ≥48 hour after delivery |
| Liver or subcapsular hematoma or severe liver injury admitted to the intensive care unit (bilirubin >6 or liver enzymes >600) | Abnormal liver function requiring extra prolonged postpartum length of stay, but not in the intensive care unit |
| Multiple coagulation abnormalities or severe hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome | Severe thrombocytopenia (<50,000) alone that does not require a transfusion or intensive care unit admission |
| Renal | |
| Diagnosis of acute tubular necrosis or treatment with renal dialysis | Oliguria treated with intravenous fluids (no intensive care unit admission) |
| Oliguria treated with multiple doses of Lasix | Oliguria treated with 1 dose of intravenous Lasix but no intensive care unit admission |
| Creatinine ≥2.0 in a woman without preexisting renal disease OR a doubling of the baseline creatinine in a woman with preexisting renal disease | |
| Sepsis | |
| Infection with hypotension with multiple liters of intravenous fluid or pressors used (septic shock) | Fever >38.5°F with elevated lactate alone without hypotension |
| Infection with pulmonary complications such as pulmonary edema or acute respiratory distress syndrome | Fever >38.5°F with presumed chorio/endometritis with elevated pulse but no other cardiovascular signs and normal lactate |
| Positive blood culture without other evidence of significant systemic illness | |
| Pulmonary | |
| Diagnosis of acute respiratory distress syndrome, pulmonary edema, or postoperative pneumonia | Administration of oxygen without a pulmonary diagnosis |
| Use of a ventilator (with either intubation or noninvasive technique) | |
| Deep vein thrombosis or pulmonary embolism | |
| Cardiac | |
| Preexisting cardiac disease (congenital or acquired) with intensive care unit admission for treatment | Preexisting cardiac disease (congenital or acquired) with intensive care unit admission for observation only |
| Peripartum cardiomyopathy | Preexisting cardiac disease (congenital or acquired) without intensive care unit admission but on labor and delivery for extra time for observation only |
| Arrhythmia that requires >1 dose of intravenous medication but not intensive care unit admission | Arrhythmia requiring 1 dose of intravenous medication but no intensive care unit admission |
| Arrhythmia that requires intensive care unit with further treatments | Arrhythmia that requires intensive care unit observation but no extra treatments |
| Intensive care unit/invasive monitoring | |
| Any intensive care unit admission that includes treatment or diagnostic or therapeutic procedure | Intensive care unit admission for observation of hypertension that does NOT require intravenous medications |
| Central line or pulmonary catheter used to monitor a complication | Intensive care unit admission for observation after general anesthesia |
| Surgical, bladder, and bowel complications | |
| Bowel or bladder injury during surgery beyond minor serosal tear | |
| Small bowel obstruction, with or without surgery during pregnancy/postpartum period | |
| Prolonged ileus for ≥4 days | Postoperative ileus that resolved without surgery in ≤3 days |
| Anesthesia complications | |
| Total spinal anesthesia | Failed spinal that requires general anesthesia |
| Aspiration pneumonia | Spinal headache treated with a blood patch |
| Epidural hematoma |
Internal review board approvals were obtained from Stanford University as the overall study host, each participating hospital for chart reviews, and the California Committee for the Protection of Human Subjects for the use of the linked data set. All cases were deidentified fully before clinical data were shared with the study team. All descriptive and statistical analyses, which included area under the receiver operating characteristic curve and C-statistic were performed using SAS software (version 9.3; SAS Institute Inc, Cary, NC).
Results
The study population consisted of 67,468 deliveries, which represented 15% of California’s births during the study period. The 16 hospitals ranged in delivery volume from 1500 to >7000 annual births. The demographic profile of the study population compared with the entire state is shown in Table 3 . Other than geographic distribution, we were not seeking to draw a representative sample of California births but rather to identify more women from regional centers and hospitals with higher African American populations.
| Characteristic | Study sample, n (%) | Statewide, n (%) |
|---|---|---|
| Total | 67,468 (100) | 474,411 (100) |
| Race/ethnicity | ||
| White | 22,937 (34.00) | 131,584 (27.74) |
| Latina | 22,657 (33.58) | 231,568 (48.81) |
| Asian | 9,050 (13.41) | 55,707 (11.74) |
| African American | 4,935 (7.31) | 27,234 (5.74) |
| Pacific Islander | 2,439 (3.62) | 15,493 (3.27) |
| Native Indian | 242 (0.36) | 2,122 (0.45) |
| Other | 59 (0.09) | 358 (0.08) |
| Refused/unknown/missing | 5,149 (7.63) | 10,345 (2.18) |
| Prepregnancy body mass index | ||
| Underweight (<18.5 kg/m 2 ) | 2,777 (4.12) | 17,684 (3.73) |
| Normal (18.5-24.9 kg/m 2 ) | 32,864 (48.71) | 197,702 (41.67) |
| Overweight (25.0-29.9 kg/m 2 ) | 14,118 (20.93) | 127,711 (29.62) |
| Obese I (30.0-34.9 kg/m 2 ) | 6,555 (9.72) | 61,876 (13.04) |
| Obese II (35.0-39.9 kg/m 2 ) | 2,699 (4.00) | 27,594 (5.82) |
| Obese III (≥40 kg/m 2 ) | 1,642 (2.43) | 16,740 (3.53) |
| Missing | 6,813 (10.1) | 25,104 (5.29) |
| Insurance | ||
| Medicaid | 25,497 (37.79) | 222,772 (46.96) |
| Private | 30,517 (45.23) | 227,493 (47.95) |
| Self-pay | 8,261 (12.24) | 14,385 (3.03) |
| Other (including government) b | 3,181 (4.71) | 9,772 (2.05) |
| Missing | 12 (0.02) | 39 (0.01) |
| Hospital neonatal intensive care unit level c | ||
| Regional | 22,942 (34.00) | 57,942 (12.21) |
| Community | 30,832 (45.70) | 238,382 (50.25) |
| Intermediate | 12,107 (17.94) | 89,990 (18.97) |
| Basic | 1,587 (2.35) | 87,397 (18.42) |
| Missing | 700 (0.15) | |
| Hospital geographic location: California | ||
| Southern | 40,750 (60.40) | 274,150 (57.79) |
| Central | 6,101 (9.04) | 50,705 (10.69) |
| Northern | 20,617 (30.56) | 149,556 (31.52) |
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