Background
Because severe maternal morbidity (SMM) is increasing in the United States, affecting up to 50,000 women per year, there was a recent call to review all mothers with SMM to better understand their morbidity and improve outcomes. Administrative screening methods for SMM have recently been shown to have low positive predictive value for true SMM after chart review. To ultimately reduce maternal morbidity and mortality we must better understand risk factors, and preventability issues about true SMM such that interventions could be designed to improve care.
Objective
Our objective was to determine risk factors associated with true SMM identified from California delivery admissions, including the relationship between SMM and preterm delivery.
Study Design
In this retrospective cohort study, SMM cases were screened for using International Classification of Diseases, Ninth Revision codes for severe illness and procedures, prolonged postpartum length of stay, intensive care unit admission, and transfusion from all deliveries in 16 hospitals from July 2012 through June 2013. Charts of screen-positive cases were reviewed and true SMM diagnosed based on expert panel agreement. Underlying disease diagnosis was determined. Women with true-positive SMM were compared to SMM-negative women for the following variables: maternal age, ethnicity, gestational age at delivery, prior cesarean delivery, and multiple gestation.
Results
In all, 491 women had true SMM and 66,977 women did not have SMM for a 0.7% rate of true SMM. Compared to SMM-negative women, SMM cases were significantly more likely to be age >35 years (33.6 vs 23.8%; P < .0001), be African American (14.1 vs 7.9%; P < .0001), have had a multiple gestation (9.7 vs 2.1%; P < .0001), and, for the multiparous women, have had a prior cesarean delivery (58 vs 30.2%; P < .0001). Preterm delivery was significantly more common in SMM women compared to SMM-negative women (41 vs 8%; P < .0001), including delivery <32 weeks (18 vs 2%; P < .0001). The most common underlying disease was obstetric hemorrhage (42%) followed by hypertensive disorders (20%) and placental hemorrhage (14%). Only 1.6% of women with SMM had cardiovascular disease as the underlying disease category.
Conclusion
An extremely high proportion of women with severe morbidity (42.5%) delivered preterm with 17.8% delivering <32 weeks, which underscores the importance of access to appropriate-level care for mothers with SMM and their newborns. Further, the extremely high rate of preterm delivery (75%) in women with placental hemorrhage in combination with their 63% prior cesarean delivery rate highlights another risk of prior cesarean delivery: subsequent preterm delivery. These data provide a reminder that a cesarean delivery could be a contributing factor to not only hemorrhage-related SMM, but also to increased subsequent preterm delivery, more reason to continue national efforts to safely reduce initial cesarean deliveries.
Introduction
It has been well documented that maternal mortality has been increasing in the United States. Because severe maternal morbidity (SMM) is on the continuum to mortality, and has similar preventable factors, it is therefore not surprising that SMM also has increased and currently complicates approximately 2% of all births affecting up to 50,000 women per year. Women with SMM are very ill and examples include women with hemorrhage requiring ≥4 U of blood, requiring admission to critical care units to manage severe illness, developing disseminated intravascular coagulation, requiring hysterectomy, and with sepsis. To ultimately reduce mortality and maternal morbidity we must better understand risk factors and preventability issues around SMM such that interventions could be designed to improve care. In line with this concept, there was a recent call to identify and review all mothers with SMM at all hospitals providing obstetric care in the United States to better understand the morbidity and improve outcomes. Several methods have been used to screen for SMM including the Centers for Disease Control and Prevention (CDC) International Classification of Diseases, Ninth Revision ( ICD-9 ) method that utilizes multiple codes associated with severe illness and the incidence estimate above was based on this methodology. However, many of these women who may have had an ICD-9 code suggesting severe illness such as a transfusion may in fact not be very ill if the chart was reviewed. In fact, a recent paper tested the validity of the CDC method by reviewing charts of screen-positive cases and reported that only 37% of the screen-positive cases actually met SMM criteria when the chart was reviewed, giving incidence of SMM of 0.9%. To better understand how to reduce true SMM the women with true morbidity must be studied, not just the women who are screen positive for SMM. As part of a larger project to validate ICD-9 diagnoses to screen for SMM, SMM cases were identified from California delivery admissions. Our objective was to determine risk factors associated with true SMM including the relationship between SMM and preterm delivery.
Materials and Methods
This retrospective cohort study was a secondary analysis of a larger study to validate the CDC ICD-9 SMM codes. The SMM cases were initially identified from all mothers delivering >20 weeks of gestation from July 1, 2012, through June 30, 2013, in 16 hospitals in California by 1 of 4 screening criteria: (1) CDC ICD-9 diagnosis for severe illness and/or procedure codes; (2) prolonged postpartum length of stay defined as 3 SD beyond the mean length of stay for the California population (4 days for a vaginal delivery and 6 days for a cesarean birth); (3) any maternal intensive care unit (ICU) admissions; and (4) administration of any blood product. The first 2 screening criteria utilized vital statistics data linked to patient discharge data and birth certificate data submitted to the California Maternal Quality Care Collaborative Data Center. The other 2 screening methods (ICU and blood administration) utilized alternate hospital data sources (charge master files, admission discharge transfer files, and blood bank data systems). These 16 hospitals were geographically representative of California but intentionally had a higher representation of perinatal centers.
Medical records of screen-positive cases were reviewed and a true SMM diagnosed based on whether the case met a clinical gold standard that was recently described in detail. Clinical gold standard criteria, organized by and based on type of morbidity (hemorrhage, hypertension, renal, sepsis, pulmonary, cardiac, ICU, surgical complications, anesthesia complication) with descriptions that denoted a very sick woman compared to someone who would not be considered severely ill, were developed by consensus with obstetric researchers experienced in quality reviews and are presented in Table 1 . These criteria were developed independently from the actual case reviews. A case was deemed a true-positive SMM if it fulfilled one of these criteria after medical record review. In all true-positive SMM the underlying disease diagnosis was determined. As an underlying disease diagnosis, hemorrhage was divided into obstetric hemorrhage defined as bleeding due to atony or vaginal or cervical lacerations, or placental defined as bleeding due to abnormal placentation such as accreta, previa, or abruption. Women with true-positive SMM were compared to the remaining women, who were either initially screen negative or did not meet the true-positive criteria after review, and will heretofore be referred to as SMM negative. The following variables were compared between groups: maternal age, ethnicity, gestational age at delivery, prior cesarean delivery, insurance, mode of delivery, prepregnancy body mass index, parity, and multiple gestation using χ 2 tests with significance level set P < .05. We performed logistic regression for SMM and preterm delivery adjusting for advanced maternal age, race, and multifetal pregnancy. All descriptive and statistical analyses were performed using software (SAS Version 9.3 (SAS Institute Inc, Cary, NC).
| Severe maternal morbidity | Not severe morbidity (insufficient evidence if this is only criteria) |
|---|---|
| Hemorrhage | |
| OB hemorrhage with ≥4 U of RBCs transfused | OB hemorrhage with 2–3 U of RBCs transfused alone |
| OB hemorrhage with 2 U of RBCs and 2 U of FFP transfused (without other procedures or complications) if not judged to be “overexuberant” transfusion | OB hemorrhage with 2 U of RBCs and 2 U of FFP transfused and judged to be “overexuberant” |
| OB hemorrhage with <4 U of blood products transfused and evidence of pulmonary congestion requiring >1 dose of furosemide | OB hemorrhage with <4 U of blood products transfused and evidence of pulmonary edema requiring only 1 dose of furosemide |
| OB hemorrhage with return to operating room for any major procedure (excludes D&C) | |
| Any emergency/unplanned peripartum hysterectomy, regardless of no. of units transfused (includes all placenta accreta) | Planned peripartum hysterectomy for cancer/neoplasia |
| OB hemorrhage with uterine artery embolization, regardless of no. of units transfused | |
| OB hemorrhage with uterine balloon or uterine compression suture placed and 2–3 U of blood products transfused | OB hemorrhage with uterine balloon or uterine compression suture placed and ≤1 U of blood products transfused |
| OB hemorrhage admitted to ICU for invasive monitoring or treatment–either medication or procedure (not just observed overnight) | Any OB hemorrhage that went to ICU for observation only without further treatment |
| Hypertension/neurologic | |
| Eclamptic seizures or epileptic seizures that were “status” | |
| Continuous infusion (IV drip) of antihypertensive medication | |
| Nonresponsiveness or loss of vision, permanent or temporary (but not momentary), documented in physician progress notes | |
| Stroke, coma, intracranial hemorrhage | |
| Preeclampsia with difficult to control severe hypertension (>160 mm Hg sBP or >110 mm Hg dBP) requiring multiple IV doses and/or persistent ≥48 h postpartum | Chronic hypertension that drifts up to severe range and needs postoperative medication dose alteration; preeclampsia: BP control with oral meds ≥48 h postpartum |
| Liver or subcapsular hematoma or severe liver injury admitted to ICU (bili >6 mg/dl or liver enzymes >600 U/L) | Abnormal liver function requiring extra PP LOS but not in ICU |
| Multiple coagulation abnormalities or severe HELLP syndrome | Severe thrombocytopenia (<50,000) alone not requiring transfusion or ICU admission |
| Renal | |
| Diagnosis of ATN or treatment with renal dialysis | Oliguria treated with IV fluids (no ICU admission) |
| Oliguria treated with multiple doses of furosemide | Oliguria treated with 1 dose of IV furosemide but no ICU admission |
| Creatinine ≥2.0 mg/dl in woman without preexisting renal disease or doubling of baseline creatinine in woman with preexisting renal disease | |
| Sepsis | |
| Infection with hypotension with multiple liters of IVF or pressors used (septic shock) | Fever >38.5 degrees C with elevated lactate alone without hypotension |
| Infection with pulmonary complications such as pulmonary edema or ARDS | Fever >38.5 degrees C 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 ARDS, pulmonary edema, or postoperative pneumonia | Administration of oxygen without pulmonary diagnosis |
| Use of ventilator (with either intubation or noninvasive technique) | |
| Deep vein thrombosis or pulmonary embolism | |
| Cardiac | |
| Preexisting cardiac disease (congenital or acquired) with ICU admission for treatment | Preexisting cardiac disease (congenital or acquired) with ICU admission for observation only |
| Peripartum cardiomyopathy | Preexisting cardiac disease (congenital or acquired) without ICU admission but on L&D for extra time for observation only |
| Arrhythmia requiring >1 dose of IV medication but not ICU admission | Arrhythmia requiring 1 dose of IV medication but no ICU admission |
| Arrhythmia requiring ICU with further treatments | Arrhythmia requiring ICU observation but no extra treatments |
| ICU/invasive monitoring | |
| Any ICU admission that includes treatment or diagnostic or therapeutic procedure | ICU admission for observation of hypertension not requiring IV meds |
| Central line or pulmonary catheter used to monitor complication | ICU admission for observation following 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 | |
| Prolonged ileus ≥4 d | Postoperative ileus that resolved without surgery in ≤3 d |
| Anesthesia complications | |
| Total spinal anesthesia | Failed spinal requiring general anesthesia |
| Aspiration pneumonia | Spinal headache treated with 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 use of the linked data set. All cases were fully deidentified before clinical data were shared with the study team.
Materials and Methods
This retrospective cohort study was a secondary analysis of a larger study to validate the CDC ICD-9 SMM codes. The SMM cases were initially identified from all mothers delivering >20 weeks of gestation from July 1, 2012, through June 30, 2013, in 16 hospitals in California by 1 of 4 screening criteria: (1) CDC ICD-9 diagnosis for severe illness and/or procedure codes; (2) prolonged postpartum length of stay defined as 3 SD beyond the mean length of stay for the California population (4 days for a vaginal delivery and 6 days for a cesarean birth); (3) any maternal intensive care unit (ICU) admissions; and (4) administration of any blood product. The first 2 screening criteria utilized vital statistics data linked to patient discharge data and birth certificate data submitted to the California Maternal Quality Care Collaborative Data Center. The other 2 screening methods (ICU and blood administration) utilized alternate hospital data sources (charge master files, admission discharge transfer files, and blood bank data systems). These 16 hospitals were geographically representative of California but intentionally had a higher representation of perinatal centers.
Medical records of screen-positive cases were reviewed and a true SMM diagnosed based on whether the case met a clinical gold standard that was recently described in detail. Clinical gold standard criteria, organized by and based on type of morbidity (hemorrhage, hypertension, renal, sepsis, pulmonary, cardiac, ICU, surgical complications, anesthesia complication) with descriptions that denoted a very sick woman compared to someone who would not be considered severely ill, were developed by consensus with obstetric researchers experienced in quality reviews and are presented in Table 1 . These criteria were developed independently from the actual case reviews. A case was deemed a true-positive SMM if it fulfilled one of these criteria after medical record review. In all true-positive SMM the underlying disease diagnosis was determined. As an underlying disease diagnosis, hemorrhage was divided into obstetric hemorrhage defined as bleeding due to atony or vaginal or cervical lacerations, or placental defined as bleeding due to abnormal placentation such as accreta, previa, or abruption. Women with true-positive SMM were compared to the remaining women, who were either initially screen negative or did not meet the true-positive criteria after review, and will heretofore be referred to as SMM negative. The following variables were compared between groups: maternal age, ethnicity, gestational age at delivery, prior cesarean delivery, insurance, mode of delivery, prepregnancy body mass index, parity, and multiple gestation using χ 2 tests with significance level set P < .05. We performed logistic regression for SMM and preterm delivery adjusting for advanced maternal age, race, and multifetal pregnancy. All descriptive and statistical analyses were performed using software (SAS Version 9.3 (SAS Institute Inc, Cary, NC).
| Severe maternal morbidity | Not severe morbidity (insufficient evidence if this is only criteria) |
|---|---|
| Hemorrhage | |
| OB hemorrhage with ≥4 U of RBCs transfused | OB hemorrhage with 2–3 U of RBCs transfused alone |
| OB hemorrhage with 2 U of RBCs and 2 U of FFP transfused (without other procedures or complications) if not judged to be “overexuberant” transfusion | OB hemorrhage with 2 U of RBCs and 2 U of FFP transfused and judged to be “overexuberant” |
| OB hemorrhage with <4 U of blood products transfused and evidence of pulmonary congestion requiring >1 dose of furosemide | OB hemorrhage with <4 U of blood products transfused and evidence of pulmonary edema requiring only 1 dose of furosemide |
| OB hemorrhage with return to operating room for any major procedure (excludes D&C) | |
| Any emergency/unplanned peripartum hysterectomy, regardless of no. of units transfused (includes all placenta accreta) | Planned peripartum hysterectomy for cancer/neoplasia |
| OB hemorrhage with uterine artery embolization, regardless of no. of units transfused | |
| OB hemorrhage with uterine balloon or uterine compression suture placed and 2–3 U of blood products transfused | OB hemorrhage with uterine balloon or uterine compression suture placed and ≤1 U of blood products transfused |
| OB hemorrhage admitted to ICU for invasive monitoring or treatment–either medication or procedure (not just observed overnight) | Any OB hemorrhage that went to ICU for observation only without further treatment |
| Hypertension/neurologic | |
| Eclamptic seizures or epileptic seizures that were “status” | |
| Continuous infusion (IV drip) of antihypertensive medication | |
| Nonresponsiveness or loss of vision, permanent or temporary (but not momentary), documented in physician progress notes | |
| Stroke, coma, intracranial hemorrhage | |
| Preeclampsia with difficult to control severe hypertension (>160 mm Hg sBP or >110 mm Hg dBP) requiring multiple IV doses and/or persistent ≥48 h postpartum | Chronic hypertension that drifts up to severe range and needs postoperative medication dose alteration; preeclampsia: BP control with oral meds ≥48 h postpartum |
| Liver or subcapsular hematoma or severe liver injury admitted to ICU (bili >6 mg/dl or liver enzymes >600 U/L) | Abnormal liver function requiring extra PP LOS but not in ICU |
| Multiple coagulation abnormalities or severe HELLP syndrome | Severe thrombocytopenia (<50,000) alone not requiring transfusion or ICU admission |
| Renal | |
| Diagnosis of ATN or treatment with renal dialysis | Oliguria treated with IV fluids (no ICU admission) |
| Oliguria treated with multiple doses of furosemide | Oliguria treated with 1 dose of IV furosemide but no ICU admission |
| Creatinine ≥2.0 mg/dl in woman without preexisting renal disease or doubling of baseline creatinine in woman with preexisting renal disease | |
| Sepsis | |
| Infection with hypotension with multiple liters of IVF or pressors used (septic shock) | Fever >38.5 degrees C with elevated lactate alone without hypotension |
| Infection with pulmonary complications such as pulmonary edema or ARDS | Fever >38.5 degrees C 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 ARDS, pulmonary edema, or postoperative pneumonia | Administration of oxygen without pulmonary diagnosis |
| Use of ventilator (with either intubation or noninvasive technique) | |
| Deep vein thrombosis or pulmonary embolism | |
| Cardiac | |
| Preexisting cardiac disease (congenital or acquired) with ICU admission for treatment | Preexisting cardiac disease (congenital or acquired) with ICU admission for observation only |
| Peripartum cardiomyopathy | Preexisting cardiac disease (congenital or acquired) without ICU admission but on L&D for extra time for observation only |
| Arrhythmia requiring >1 dose of IV medication but not ICU admission | Arrhythmia requiring 1 dose of IV medication but no ICU admission |
| Arrhythmia requiring ICU with further treatments | Arrhythmia requiring ICU observation but no extra treatments |
| ICU/invasive monitoring | |
| Any ICU admission that includes treatment or diagnostic or therapeutic procedure | ICU admission for observation of hypertension not requiring IV meds |
| Central line or pulmonary catheter used to monitor complication | ICU admission for observation following 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 | |
| Prolonged ileus ≥4 d | Postoperative ileus that resolved without surgery in ≤3 d |
| Anesthesia complications | |
| Total spinal anesthesia | Failed spinal requiring general anesthesia |
| Aspiration pneumonia | Spinal headache treated with blood patch |
| Epidural hematoma |
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