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Injury-related maternal mortality

      Objective

      Prior studies on maternal mortality largely focused on deaths in the conventional time frame of 42 days after a live-birth delivery, often excluding women with a stillbirth.
      • Cristina Rossi A.
      • Mullin P.
      The etiology of maternal mortality in developed countries: a systematic review of literature.
      Others relied on a pregnancy checkbox on the death certificate and then submitted to a central repository
      • MacDorman M.F.
      • Declercq E.
      • Thoma M.E.
      Trends in maternal mortality by sociodemographic characteristics and cause of death in 27 states and the District of Columbia.
      or did not evaluate injury,
      • Schutte J.M.
      • Steegers E.A.
      • Schuitemaker N.W.
      • et al.
      Rise in maternal mortality in The Netherlands.
      which has emerged as an important cause of late maternal death 43–365 days postpartum.
      • Thornton C.
      • Schmied V.
      • Dennis C.L.
      • Barnett B.
      • Dahlen H.G.
      Maternal deaths in NSW (2000–2006) from nonmedical causes (suicide and trauma) in the first year following birth.
      Herein we included stillbirths and provided more discrete time intervals to evaluate injury-specific causes of maternal mortality.

      Study Design

      We studied live births and stillbirths from 20 weeks’ gestation onward, from 1990 through 2015, in Ontario, Canada, where health care is universally available. Provincial databases of all hospital deliveries and Vital Statistics, including mandatory completed death certificates,
      • Chiu M.
      • Lebenbaum M.
      • Lam K.
      • et al.
      Describing the linkages of the immigration, refugees and citizenship Canada permanent resident data and vital statistics death registry to Ontario's administrative health database.
      were linked using unique encoded identifiers at the Institute for Clinical Evaluative Sciences. The Research Ethics Board of the Sunnybrook Health Sciences Centre granted ethics approval. Incidence rates (IRs) were separately calculated for injury and noninjury maternal deaths. IRs were shown across 11 time intervals within the 365 days after birth: biweekly from 0 to 42 days (when deaths are most common) and every 6 weeks thereafter. To account for the changing number of women at risk in each interval and the time at risk therein, IRs were presented per 1 million person-weeks, with 95% confidence intervals (CIs). The proportion of deaths caused by injury in each interval was also calculated and the corresponding trend tested by a 2-sided Cochrane-Armitage test. Maternal deaths caused by injury at 0–42 and 43–365 days were presented by injury subtype: transport accident (International Classification of Diseases, ninth edition [ICD-9] E800–E849); accidental poisoning/overdose (ICD-9 E850–E854); intentional self-harm (ICD-9 E950–E959); assault/homicide (ICD-9 E960–E969); or other (ICD-9 E855–E949 and E970–E999).

      Results

      Of 3,179,157 births, there were 760 maternal deaths within 365 days of delivery (23.9 per 100,000, 95% CI, 22.2–25.6), including 720 deaths among 3,159,762 livebirths (22.8 per 100,000, 95% CI, 21.1–24.5), and 40 deaths among 19,395 stillbirths (206.2 per 100,000, 95% CI, 142.4–270.1). There were 235 maternal deaths within 42 days of birth (IR, 12.3 per 1 million person-weeks, 95% CI, 10.7–14.0) and 525 deaths from 43 to 365 days (IR, 3.6 per 1 million person-weeks, 95% CI, 3.3–3.9) (Figure 1, bars). In the first 14 days after birth, injuries caused 4.1% of maternal deaths; by 28 days, they accounted for 35–48% of all deaths (P < .001) (Figure 1, top red). Greater than 60% of injury-related deaths were from self-harm, poisoning/overdose, and homicide (Figure 1, bottom circles).
      Figure thumbnail gr1
      Figure 1Maternal mortality incidence rates for injury and noninjury deaths
      Maternal mortality incidence rates for injury (orange bars) and noninjury (blue bars) deaths occurring at various intervals from birth to 42 days (early deaths) and from 43 to 365 days (late deaths). Incidence rates and 95% confidence intervals (CI) are presented per 1 million person-weeks by women at risk in the denominators. The proportion of deaths caused by injury are shown in each time interval and tested by the Cochrane-Armitage test for trend (top red). Injury-related deaths are further broken down by subtype at 0–42 and 43–365 days (lower circles).
      Ray JG. Injury-related maternal mortality. Am J Obstet Gynecol 2018.

      Conclusion

      Greater than 95% of maternal deaths before 14 days postpartum were due to noninjury causes, as described elsewhere.
      • Cristina Rossi A.
      • Mullin P.
      The etiology of maternal mortality in developed countries: a systematic review of literature.
      • MacDorman M.F.
      • Declercq E.
      • Thoma M.E.
      Trends in maternal mortality by sociodemographic characteristics and cause of death in 27 states and the District of Columbia.
      • Schutte J.M.
      • Steegers E.A.
      • Schuitemaker N.W.
      • et al.
      Rise in maternal mortality in The Netherlands.
      Thereafter, injury-related deaths rose significantly, with more than one third of injuries being intentional, a similar proportion to that in a study of 129 maternal deaths in Australia.
      • Thornton C.
      • Schmied V.
      • Dennis C.L.
      • Barnett B.
      • Dahlen H.G.
      Maternal deaths in NSW (2000–2006) from nonmedical causes (suicide and trauma) in the first year following birth.
      This study did not capture out-of-hospital births, which are less than 1% of births in Ontario, or maternal deaths occurring antepartum. Although direct and indirect causes of death were not differentiated herein, the striking difference in maternal mortality rates following a stillbirth vs a livebirth deserves further study. Future studies should further classify maternal deaths by injury subtypes, including overdoses, and additionally evaluate antepartum deaths.

      Acknowledgment

      Author contributions included the following: Joel G. Ray and Allison L. Park developed the study concept, analysis and interpretation of the data, drafting of the manuscript, manuscript revision, and approval of final version. Jonathan Zipursky was responsible for the interpretation of the data, manuscript revision, and approval of final version.

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