Background
The Centers for Disease Control and Prevention has reported a steady increase in the US pregnancy-related mortality ratio since national surveillance began in 1987, although trends are partially induced by concurrent improvements in the identification of pregnancy-related deaths. No previous work has evaluated pregnancy-associated and pregnancy-related deaths among active-duty service members, a population with comprehensive health coverage and stable employment.
Objective
This study aimed to assess trends and variations in pregnancy-associated and pregnancy-related deaths in the US military.
Study Design
Live births to active-duty service members were captured in Department of Defense Birth and Infant Health Research program data from 2003 to 2014. Pregnancy-associated deaths (deaths temporally related to pregnancy from any cause) were identified through 1 year after pregnancy end date using National Death Index Plus data from the Joint Department of Defense and Department of Veterans Affairs Suicide Data Repository. Pregnancy-associated deaths were classified as pregnancy-related (causally related to pregnancy) based on cause-of-death codes in the National Death Index Plus data, administrative medical encounter data, and medical record review. Pregnancy-related deaths were reported including and excluding deaths from suicide and unintentional overdose. Mortality ratios (deaths per 100,000 live births) were reported overall, triennially, and by selected characteristics; the relative contribution of each cause of death to all pregnancy-associated deaths was reported overall and by age, race and ethnicity, and marital status. Timing of death relative to pregnancy end date was assessed by cause of death.
Results
A total of 179,252 live births occurred to active-duty service members from 2003 to 2014. Pregnancy-associated and pregnancy-related mortality ratios were 41.3 (95% confidence interval, 32.4–51.8) and 18.4 (95% confidence interval, 12.7–25.9), respectively. Excluding deaths from suicide and unintentional overdose, the pregnancy-related mortality ratio was 11.2 (95% confidence interval, 6.8–17.2). Deaths from suicide and unintentional overdose composed a larger proportion of pregnancy-related deaths over time and accounted for 17.6% of all pregnancy-associated deaths. Deaths from other pregnancy-related causes accounted for a greater share of deaths among older vs younger service members (≥30 years: 41.2%; 18–29 years: 22.8%) and non-Hispanic Black vs White service members (33.3% vs 24.1%). Pregnancy-related deaths, excluding suicide and unintentional overdose, were more likely to occur within 42 days of pregnancy end date; in contrast, deaths from suicide, overdose, assault, and undetermined intent were more likely to occur between 42 days and 1 year after pregnancy.
Conclusion
Pregnancy-associated and pregnancy-related deaths varied over time and by age and race and ethnicity. Suicide and overdose are major recent causes of pregnancy-related death among active-duty service members.
Introduction
The Centers for Disease Control and Prevention (CDC) national Pregnancy Mortality Surveillance System has documented an increase in pregnancy-related mortality (deaths causally related to pregnancy or its management) in the US over the last 3 decades. This increase has been attributed to several factors, including delayed childbearing and higher rates of obesity and cardiovascular conditions ; however, recent evidence suggested that the rise since 2003 may be explained by improved capture of pregnancy-related deaths via the pregnancy checkbox on death certificates. Examination of the cause of death among all pregnancy-associated deaths (deaths temporally related to pregnancy from any cause) has elucidated other trends: the contribution of hemorrhage and hypertensive disorders has declined, whereas deaths from overdose and suicide are emerging. Estimates of the latter causes’ prevalence and relative contribution to overall pregnancy-associated and pregnancy-related deaths remain limited because of frequent undercounting of pregnancy-associated deaths from nonobstetrical causes, including suicide, overdose, and homicide.
Why was this study conducted?
This study aimed to assess pregnancy-associated and pregnancy-related deaths among US service members and evaluate characteristics associated with specific causes and timing of death.
Key findings
From 2003 to 2014, pregnancy-related deaths from direct obstetrical causes declined, whereas deaths from suicide and unintentional overdose, particularly prevalent among non-Hispanic White service members, increased. Timing of death relative to pregnancy skewed later during the postpartum period for deaths from suicide, unintentional overdose, assault, and undetermined intent, with some variation by pregnancy outcome.
What does this add to what is known?
This study assessed pregnancy-associated and pregnancy-related deaths among US service members, a selectively healthy population with comprehensive health coverage. Moreover, this study has offered a unique comparison of the characteristics associated with deaths from suicide and unintentional overdose vs other pregnancy-related causes.
Disparities in pregnancy-related deaths are well-established nationally and at the state level. Non-Hispanic Black women have a pregnancy-related mortality ratio 3 to 4 times higher than non-Hispanic White women; disparities persist with some variation across age groups, geographic regions, and education levels. , , In contrast, pregnancy-associated deaths from overdose and suicide are more likely to occur among non-Hispanic White women. Although less well documented, unmarried women were found to have higher pregnancy-related and maternal mortality ratios than married women. ,
No previous work has examined pregnancy-associated and pregnancy-related deaths, captured through 1 year after pregnancy, among active-duty service members. This population is distinct from their civilian counterparts as they are guaranteed free, comprehensive health coverage and stable employment and tend to have lower rates of chronic medical conditions. Despite these protective factors, a study conducted among service members from 2003 to 2015 reported a stark rise in severe maternal morbidity, an important risk factor for pregnancy-related death, and persistent racial and ethnic disparities. Moreover, service members endure unique work-related stressors (eg, frequent relocation or deployment), which may increase the risk of onset, exacerbation, or relapse of mental health conditions and associated mortality during pregnancy and after delivery. , ,
This study leveraged data from the Department of Defense (DoD) Birth and Infant Health Research (BIHR) program to assess pregnancy-associated and pregnancy-related deaths among US service members and evaluate characteristics associated with specific causes and timing of death.
Materials and Methods
Study population
We identified active-duty US military service members captured in DoD BIHR program data with a live birth or pregnancy loss from 2002 to 2014. Details regarding BIHR data and methodologies have been outlined previously ; briefly, data include personnel and demographic information from the Defense Manpower Data Center and administrative medical encounter data from the Military Health System (MHS) Data Repository. MHS care is delivered at military treatment facilities (MTFs) and civilian facilities in the US and overseas. Medical data span inpatient and outpatient encounters and are coded with International Classification of Diseases, Ninth or Tenth Revision, Clinical Modification (ICD-9-CM or ICD-10-CM) diagnosis and procedure codes and Current Procedural Terminology codes, which are used to identify pregnancies. Same-sex multiples are excluded because of difficulties distinguishing their neonatal records. Institutional review board approval was obtained from the Naval Health Research Center (protocol number NHRC.1999.0003) and informed consent was waived as per 32 Code of Federal Regulations § 219.116(d).
Outcome measures
Using the service members’ Social Security number and associated pregnancy records, deaths occurring from 2003 to 2014 were identified in the National Death Index Plus (NDI+) data from the Joint DoD and Department of Veterans Affairs Suicide Data Repository. NDI+ data contains death certificate information, including cause-of-death codes, reported by state vital statistics offices. Moreover, information on US military personnel deaths occurring outside of the country was recently added to NDI+ data. Deaths were linked to a documented pregnancy if they occurred during pregnancy or within 1 year after pregnancy end date. If the associated pregnancy did not end in a live birth, administrative medical encounter data and electronic medical records were reviewed to verify the timing of death relative to pregnancy. If a pregnancy could not be confirmed, the death was not considered for further analysis.
Pregnancy-associated death is the death of a person while pregnant or within 1 year after pregnancy end date, regardless of cause. Pregnancy-related death is the death of a person while pregnant or within 1 year after pregnancy end date from any cause related to or aggravated by pregnancy. Pregnancy-associated deaths were assigned a cause and classified as pregnancy related, based on the causes of death per the death certificate, administrative medical encounter data, and electronic medical records. Despite CDC treatment of deaths from suicide, overdose, and unintentional injuries related to a mental health condition and temporally connected to pregnancy as pregnancy related, literature incorporating this definition is limited. , We employed definitions for pregnancy-related death that included and excluded deaths from suicide and unintentional overdose to (1) draw comparisons with studies using either definition and (2) contrast characteristics associated with either definition.
Explanatory variables
Age (18–29 or ≥30 years) was determined on the basis of the pregnancy end date. Race and ethnicity (non-Hispanic Black, non-Hispanic White, or other or unknown), marital status (married or unmarried or unknown), service branch (Air Force, Army, Coast Guard, Marine Corps, or Navy), and rank (junior enlisted, senior enlisted, or officer), an indicator of socioeconomic status, were ascertained from military personnel files. Location of birth (MTF or civilian hospital) was obtained from birth or delivery records. Career deployment history was ascertained through 1 year after pregnancy (ever or never deployed) and within pregnancy or 1 year after pregnancy (yes or no). Psychiatric and substance use disorders were defined using ICD-9-CM or ICD-10-CM diagnosis codes ( Supplemental Table ) on health records spanning pregnancy to 1 year after pregnancy.
Statistical analysis
The pregnancy-related mortality ratio (deaths per 100,000 live births) and relative percentage of pregnancy-related deaths from suicide and unintentional overdose were calculated throughout the study period (in 3-year increments). Pregnancy-associated and pregnancy-related mortality ratios were calculated overall and by selected characteristics. Ratios based on fewer than 5 deaths were suppressed. The Poisson distribution was used to calculate exact 95% confidence intervals (CIs). The relative contribution of each cause of death to all pregnancy-associated deaths was reported overall and by age, race and ethnicity, and marital status. Timing of death relative to pregnancy was examined among pregnancy-related deaths and all violent deaths (ie, suicide, assault, and undetermined intent) and deaths from unintentional overdose. Data management was performed using SAS (version 9.4 SAS Institute, Cary, NC); mortality ratios and 95% CIs were calculated in R (version 3.5.2; https://cran.r-project.org/bin/windows/base/old/3.5.2/ ), using the epitools package.
Results
A total of 179,252 live births occurred to active-duty service members from 2003 to 2014. There were 81 potential pregnancy-related deaths: 7 could not be associated with a pregnancy in the previous year, 41 were pregnancy associated but not related, and 33 were pregnancy related (including deaths from suicide and unintentional overdose). Of the 33 pregnancy-related deaths, 13 were from suicide (n=10) or unintentional overdose (n=3). Most pregnancy-associated and pregnancy-related deaths followed a live birth (74.3% and 72.7%, respectively). Excluding deaths from suicide and unintentional overdose, 95.0% of pregnancy-related deaths followed a live birth; only 68.4% of these deaths were indicated by disposition status in the medical record.
Pregnancy-related mortality ratios and contributing causes varied over time: the proportion of pregnancy-related deaths from suicide and unintentional overdose increased from 2003 to 2014, whereas deaths from other pregnancy-related causes (eg, infection or cardiovascular conditions) decreased ( Figure 1 ). Overall pregnancy-associated and pregnancy-related mortality ratios were 41.3 (95% CI, 32.4–51.8) and 18.4 (95% CI, 12.7–25.9), respectively ( Table ). Excluding deaths from suicide and unintentional overdose, the pregnancy-related mortality ratio was 11.2 (95% CI, 6.8–17.2). Pregnancy-associated mortality ratios for suicide and assault were 5.6 (95% CI, 2.7–10.3) and 3.9 (95% CI, 1.6–8.0), respectively. Mortality ratios varied by selected demographic characteristics, although CIs were wide and overlapping ( Table ). Individuals aged ≥30 years had higher pregnancy-related mortality ratios than those aged 18 to 29 years (21.5 vs 17.5), while ratios were relatively comparable between those who identified as non-Hispanic Black and those who identified as non-Hispanic White (18.7 vs 17.6). Excluding deaths from suicide and unintentional overdose widened differences, particularly for non-Hispanic Black vs non-Hispanic White service members (16.6 vs 8.2). The pregnancy-related mortality ratio was higher among individuals with unmarried or unknown marital status relative to married individuals (30.9 vs 13.8), although differences partially attenuated when deaths from suicide and unintentional overdose were excluded (16.5 vs 9.2). There was little variation in mortality ratios between service members who were ever deployed and service members who were never deployed; assessment by deployment status during pregnancy or up to 1 year after pregnancy was limited by low case count. Pregnancy-related mortality ratios, excluding deaths from suicide and unintentional overdose, were higher among service members delivering at civilian facilities vs MTFs (12.8 vs 9.6).
| Characteristic | Live births | Pregnancy-associated mortality | Pregnancy-related mortality | ||||
|---|---|---|---|---|---|---|---|
| Including suicide and unintentional overdose | Excluding suicide and unintentional overdose | ||||||
| Deaths | Mortality ratio (95% CI) | Deaths | Mortality ratio (95% CI) | Deaths | Mortality ratio (95% CI) | ||
| Overall | 179,252 | 74 | 41.3 (32.4–51.8) | 33 | 18.4 (12.7–25.9) | 20 | 11.2 (6.8–17.2) |
| Age at pregnancy end date (y) | |||||||
| 18–29 | 137,325 | 57 | 41.5 (31.4–53.8) | 24 | 17.5 (11.2–26.0) | 13 | 9.5 (5.0–16.2) |
| ≥30 | 41,927 | 17 | 40.5 (23.6–64.9) | 9 | 21.5 (9.8–40.7) a | 7 | 16.7 (6.7–34.4) a |
| Race and ethnicity | |||||||
| Non-Hispanic Black | 48,213 | 24 | 49.8 (31.9–74.1) | 9 | 18.7 (8.5–35.4) a | 8 | 16.6 (7.2–32.7) a |
| Non-Hispanic White | 85,211 | 29 | 34.0 (22.8–48.9) | 15 | 17.6 (9.9–29.0) | 7 | 8.2 (3.3–16.9) a |
| Other or unknown | 45,828 | 21 | 45.8 (28.4–70.0) | 9 | 19.6 (9.0–37.3) a | 5 | 10.9 (3.5–25.5) a |
| Marital status | |||||||
| Married | 130,690 | 43 | 32.9 (23.8–44.3) | 18 | 13.8 (8.2–21.8) | 12 | 9.2 (4.7–16.0) |
| Unmarried or unknown | 48,562 | 31 | 63.8 (43.4–90.6) | 15 | 30.9 (17.3–50.9) | 8 | 16.5 (7.1–32.5) a |
| Service branch | |||||||
| Air Force | 53,985 | 25 | 46.3 (30.0–68.4) | 11 | 20.4 (10.2–36.5) a | 5 | 9.3 (3.0–21.6) a |
| Army | 60,876 | 25 | 41.1 (26.6–60.6) | 13 | 21.4 (11.4–36.5) | 8 | 13.1 (5.7–25.9) a |
| Coast Guard | 3935 | 1 | — b | 0 | — b | 0 | — b |
| Marine Corps | 13,583 | 5 | 36.8 (12.0–85.9) a | 2 | — b | 1 | — b |
| Navy | 46,873 | 18 | 38.4 (22.8–60.7) | 7 | 14.9 (6.0–30.8) a | 6 | 12.8 (4.7–27.9) a |
| Rank | |||||||
| Junior enlisted | 92,507 | 46 | 49.7 (36.4–66.3) | 17 | 18.4 (10.7–29.4) | 10 | 10.8 (5.2–19.9) a |
| Senior enlisted | 62,166 | 21 | 33.8 (20.9–51.6) | 13 | 20.9 (11.1–35.8) | 7 | 11.3 (4.5–23.2) a |
| Officer | 24,579 | 7 | 28.5 (11.5–58.7) a | 3 | — b | 3 | — b |
| Deployment history | |||||||
| Never deployed | 102,985 | 46 | 44.7 (32.7–59.6) | 19 | 18.4 (11.1–28.8) | 12 | 11.7 (6.0–20.4) |
| Ever deployed | 76,267 | 28 | 36.7 (24.4–53.1) | 14 | 18.4 (10.0–30.8) | 8 | 10.5 (4.5–20.7) a |
| Deployment during pregnancy or up to 1 year after pregnancy | |||||||
| No | 163,041 | 64 | 39.3 (30.2–50.1) | 30 | 18.4 (12.4–26.3) | 18 | 11.0 (6.5–17.4) |
| Yes | 16,211 | 10 | 61.7 (29.6–113.4) a | 3 | — b | 2 | — b |
| Psychiatric or substance use disorder c | |||||||
| No | 152,202 | 56 | 36.8 (27.8–47.8) | 26 | 17.1 (11.2–25.0) | 18 | 11.8 (7.0–18.7) |
| Yes | 27,050 | 18 | 66.5 (39.4–105.2) | 7 | 25.9 (10.4–53.3) a | 2 | — b |
| Location of birth d | |||||||
| Military treatment facility | 124,426 | 35 | 28.1 (19.6–39.1) | 15 | 12.1 (6.7–19.9) | 12 | 9.6 (5.0–16.8) |
| Civilian hospital | 54,826 | 20 | 36.5 (22.3–56.3) | 9 | 16.4 (7.5–31.2) a | 7 | 12.8 (5.1–26.3) a |
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