Abstract
Most studies of severe maternal morbidity (SMM) only include cases that occur during birth hospitalizations. We examined the increase in cases when including severe maternal morbidity during antenatal and postpartum (within 42 days of discharge) hospitalizations, using longitudinally linked data from 1,010,250 births in California from 9/1/2016-12/31/2018. For total SMM, expanding the definition resulted in 22.8% more cases; for non-transfusion SMM, 45.1% more cases were added. Sepsis accounted for 55.5% of the additional cases. The increase varied for specific indicators, e.g., <2% for amniotic fluid embolism, 7.0% for transfusion, 112.9% for sepsis, and 155.6% for acute myocardial infarction. These findings reiterate the importance of considering SMM beyond just the birth hospitalization and access to longitudinally linked data to facilitate a more complete understanding of SMM.
Precis:
Longitudinally linked antepartum and postpartum hospitalization data increased ascertainment of severe maternal morbidity.
Introduction.
Most studies of severe maternal morbidity (SMM) only include cases that occur during birth hospitalizations. Declercq et al. recently reported that including cases that emerge during antenatal and postpartum hospitalizations increased SMM by 21.9%.1 Our objective was to replicate Declercq’s analysis using similar longitudinally linked hospital discharge data from a larger sample to estimate the increase in SMM when considering both antepartum and postpartum events rather than the birth hospitalization alone.
Methods.
We examined 1,010,250 births (live births and stillbirths), using the same time period of births (9/1/2016-12/31/2018), SMM definition (ie, Centers for Disease Control and Prevention index),3 and hospitalization definitions as Declerq and colleagues. Data were from California vital records linked with maternal hospital discharge records. We first counted SMM cases at birth hospitalization, then added unique antepartum cases (i.e., occurred during pregnancy and discharged at least 1 day before admittance to birth hospitalization), and then added unique postpartum cases (i.e., admitted 1 to 42 days after discharge from birth hospitalization). We determined numbers and rates of SMM cases per 10,000 births and percent contribution to the SMM rate for each type of hospitalization, for total SMM, non-transfusion SMM, and each specific SMM indicator. We included examination of cases added when only considering non-transfusion SMM (i.e., excluding cases for which transfusion was the only qualifying indicator) because transfusion codes may overestimate SMM but are important for identification of hemorrhage-related SMM.3,4 Analyses were approved by the California Committee for the Protection of Human Subjects.
Results.
Among the individuals who gave birth, 48% were Hispanic, 27% non-Hispanic White, 16% Asian or Pacific Islander, and 5% Black; 46% had some college education; 50% had private insurance; 73% were age 20-34 years; 38% were nulliparous; and 31% had cesarean births. We observed 23,118 SMM cases (12,418 non-transfusion cases). For total SMM, expanding the SMM definition resulted in 22.8% more cases (10.7% antenatal, 12.1% postpartum) (Table 1). For non-transfusion SMM, it resulted in 45.1% more cases (20.9% antenatal, 24.2% postpartum). Ninety percent of added cases were non-transfusion SMM (38.3 of the 42.5 total cases added per 100,000 births). Sepsis accounted for 55.5% of added cases (23.6 of the 42.5 total cases added per 100,000 births). The increase in cases per indicator varied widely, e.g., <2% for amniotic fluid embolism, 7.0% for transfusion, 112.9% for sepsis, and 155.6% for acute myocardial infarction.
Table 1.
Rate of total SMM, non-transfusion SMM, and SMM indicators during antenatal, birth and postpartum hospitalizations and additional percent of cases added by including antenatal and postpartum hospitalizations, California births from 9/1/2016-12/31/2018*
| Rate (95% CI) per 10,000 birth hospitalizations |
Cases added per indicator by including non-birth hospitalization % (n) |
||||
|---|---|---|---|---|---|
| SMM Indicator | Antenatal | Birth | Postpartum | Total cases added: antenatal and postpartum [% of total] |
|
| Total SMM | 19.8 (19.0 - 20.7) | 186.4 (183.7 - 189.0) | 22.6 (21.7 - 23.5) | 42.5 (38.6-46.5) [100] | 22.8 (4290) |
| Non-transfusion SMM | 17.7 (16.9 - 18.5) | 84.7 (82.9 - 86.5) | 20.5 (19.6 - 21.4) | 38.3 (35.5-41.1) [89.9] | 45.1 (3861) |
| Acute renal failure | 2.1 (1.8 - 2.4) | 13.8 (13.0 - 14.5) | 2.8 (2.4 - 3.1) | 4.9 (3.7-6.0) [11.5] | 35.3 (491) |
| Cardiac arrest | <0.1 | 0.8 (0.7 - 1.0) | <0.1 | <0.1 [<1] | <15 (n.r.) |
| Heart failure during surgery | <0.1 | 0.1 (0.1 - 0.2) | <0.1 | <0.1[<1] | <15 (n.r.) |
| Shock | 0.2 (0.1 - 0.3) | 5.4 (5.0 - 5.9) | 0.5 (0.4 - 0.7) | 0.7 (0.0-1.4) [1.7] | 13.2 (72) |
| Sepsis | 11.7 (11.1 - 12.4) | 20.9 (20.0 - 21.8) | 11.9 (11.2 - 12.5) | 23.6 (22.0-25.2) [55.6] | 112.9 (2386) |
| Disseminated intravascular coagulation | 0.6 (0.5 - 0.8) | 23.9 (23.0 - 24.9) | 1.5 (1.3 - 1.7) | 2.1 (0.7-3.5) [5.0] | 8.8 (213) |
| Amniotic fluid embolism | <0.1 | 0.6 (0.5 - 0.8) | 0 | <0.1 [<1] | <5 (n.r.) |
| Thrombotic embolism | 0.8 (0.6 - 1.0) | 2.4 (2.1 - 2.7) | 1.8 (1.6 - 2.1) | 2.6 (2.1-3.2) [6.1] | 109.1 (265) |
| Puerperal cerebrovascular disorders | 1.0 (0.8 - 1.2) | 2.6 (2.3 - 2.9) | 1.3 (1.1 - 1.6) | 2.3 (1.8-2.9) [5.4] | 88.3 (233) |
| Severe anesthesia complications | 0 | 0.1 (0.0 - 0.1) | <0.1 | 0.1 (0.0-0.3) [<1] | n.r. (<15) |
| Pulmonary edema | 0.7 (0.5 - 0.8) | 6.3 (5.8 - 6.8) | 2.9 (2.5 - 3.2) | 3.5 (2.7-4.3) [8.2] | 56.0 (357) |
| Adult respiratory distress syndrome | 2.9 (2.6 - 3.2) | 9.7 (9.1 - 10.3) | 2.2 (1.9 - 2.5) | 5.1 (4.1-6.1) [12.0] | 53.0 (517) |
| Acute myocardial infarction | 0.1 (0.1 - 0.2) | 0.4 (0.2 - 0.5) | 0.4 (0.3 - 0.6) | 0.6 (0.3-0.8) [1.4] | 155.6 (56) |
| Eclampsia | 0.1 (0.0 - 0.1) | 6.7 (6.2 - 7.2) | 1.0 (0.8 - 1.2) | 1.1 (0.3-1.8) [2.6] | 16.5 (111) |
| Sickle cell anemia | 0.3 (0.2 - 0.4) | 0.3 (0.2 - 0.4) | 0 | 0.3 (0.1-0.5) [<1] | 88.2 (30) |
| Aneurysm | <0.1 | 0.2 (0.1 - 0.3) | <0.1 | <0.1 [<1] | <25 (n.r.) |
| Ventilation | 0.9 (0.7 - 1.1) | 4.8 (4.4 - 5.2) | 0.7 (0.5 - 0.8) | 1.5 (0.9-2.2) [3.5] | 32.1 (156) |
| Hysterectomy | 0.1 (0.0 - 0.2) | 12.4 (11.7 - 13.1) | 0.7 (0.5 - 0.8) | 0.8 (0.0-1.8) [1.9] | 6.3 (79) |
| Temporary tracheostomy | <0.1 | <0.1 | <0.1 | <0.1 [<1] | 100.0 (n.r.) |
| Conversion of cardiac rhythm | 0.2 (0.1 - 0.3) | 0.9 (0.7 - 1.1) | <0.1 | 0.3 (0.0-0.5) [<1] | 28.6 (26) |
| Transfusion | 3.8 (3.4 - 4.2) | 122.0 (119.8 - 124.1) | 4.7 (4.3 - 5.1) | 8.5 (5.4-11.6) [20.0] | 7.0 (859) |
Values are approximated or not reported for cells that involve fewer than 11 cases per agreement with guidelines from the California Department of Health Care Access and Information.
n.r. = not reportable
Discussion.
For total SMM, 1 in 5 SMM cases are missed when excluding those that occur before or after the birth hospitalization, which is consistent with Declercq’s prior publication.1 When considering non-transfusion SMM, almost 1 in 2 cases are missed. The importance of expanding surveillance to include antenatal and postpartum hospitalizations varied widely across indicators; notably, case counts more than doubled for sepsis, thrombotic embolism, and acute myocardial infarction. Further, over half of all missed cases had sepsis. Our results also suggest that over-estimation of SMM by inclusion of transfusion as a defining indicator is less marked for cases that emerge during antenatal or postpartum (versus birth) hospitalizations, as inclusion of antepartum and postpartum events only added 7.0% more cases. Our prior analysis of California births from 2008-2012 based on ICD-9 codes similarly found that inclusion of postpartum readmissions up to 42 days after delivery added 12.1% more SMM cases.5 Another study reported that postpartum readmissions within 30 days added 14.4% more cases within a privately insured population and 31.0% more within a Medicaid-insured population.6 Another study of a privately insured population reported 34% more total SMM cases and 54% more non-transfusion cases after including readmissions within 42 days postpartum.7 Understanding what explains variability across studies is important but beyond our scope. Regardless, all of these findings reiterate the importance of considering SMM beyond just the birth hospitalization and of facilitating availability of longitudinally linked hospitalization data to improve current understanding of SMM.1,2,4
Supplementary Material
Funding:
NR017020, NR020335 and UG3 HD108053
REFERENCES
- 1.Declercq ER, Cabral HJ, Cui X, Liu CL, Amutah-Onukagha N, Larson E, Meadows A, Diop H. Using Longitudinally Linked Data to Measure Severe Maternal Morbidity.Obstet Gynecol 2022. Feb 1;139(2):165–171. doi: 10.1097/AOG.0000000000004641 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Callaghan WM. Identifying Cases of Severe Maternal Morbidity: Moving Beyond the Delivery Hospitalization. Obstet Gynecol 2022. Feb 1;139(2):163–164. doi: 10.1097/AOG.0000000000004665 [DOI] [PubMed] [Google Scholar]
- 3.Main EK, Abreo A, McNulty J, Gilbert W, McNally C, Poeltler D, Lanner-Cusin K, Fenton D, Gipps T, Melsop K, Greene N, Gould JB, Kilpatrick S. Measuring severe maternal morbidity: validation of potential measures. Am J Obstet Gynecol 2016. May;214(5):643.e1–643.e10. doi: 10.1016/j.ajog.2015.11.004 [DOI] [PubMed] [Google Scholar]
- 4.Carmichael SL, Abrams B, El Ayadi A, Lee HC, Liu C, Lyell DJ, Lyndon A, Main EK, Mujahid M, Tian L, Snowden JM. Ways Forward in Preventing Severe Maternal Morbidity and Maternal Health Inequities: Conceptual Frameworks, Definitions, and Data, from a Population Health Perspective. Womens Health Issues 2021. Dec 28:S1049-3867(21)00181-X. doi: 10.1016/j.whi.2021.11.006 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Girsen AI, Sie L, Carmichael SL, Lee HC, Foeller ME, Druzin ML, Gibbs RS. Rate and causes of severe maternal morbidity at readmission: California births in 2008-2012. J Perinatol 2020. Jan;40(1):25–29. doi: 10.1038/s41372-019-0481-z [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Black CM, Vesco KK, Mehta V, Ohman-Strickland P, Demissie K, Schneider D. Hospital Readmission Following Delivery With and Without Severe Maternal Morbidity. J Womens Health (Larchmt) 2021. Dec;30(12):1736–1743. doi: 10.1089/jwh.2020.8815 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Admon LK, Dalton VK, Kolenic GE, Tilea A, Hall SV, Kozhimannil KB, Zivin K. Comparison of Delivery-Related, Early and Late Postpartum Severe Maternal Morbidity Among Individuals With Commercial Insurance in the US, 2016 to 2017. JAMA Netw Open 2021. Dec 1;4(12):e2137716. doi: 10.1001/jamanetworkopen.2021.37716 [DOI] [PMC free article] [PubMed] [Google Scholar]
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