The National Center for Health Statistics (NCHS) reported an 18.4% increase in US maternal mortality (ie, death during pregnancy or within 42 days of pregnancy) between 2019 and 2020. The relative increase was 44.4% among Hispanic, 25.7% among non-Hispanic Black, and 6.1% among non-Hispanic White women.1 Given a 16.8% increase in overall US mortality in 2020, largely attributed to the COVID-19 pandemic,2 we examined the pandemic’s role in 2020 maternal death rates.
This study was exempt from review under the US Department of Health and Human Services regulation for secondary data analysis; consent was not required for vital records. We followed the STROBE reporting guideline.
We used deidentified NCHS mortality and natality files from 2018 to 2020. We limited analyses to maternal deaths (International Statistical Classification of Diseases and Related Health Problems, Tenth Revision [ICD-10] codes A34, O00-O95, and O98-O99) based on underlying cause of death in accordance with NCHS guidelines.3 None of these ICD-10 codes exclusively identify COVID-19 (ICD-10 U07.1) as the cause even when COVID-19 was a factor in maternal death (eMethods in the Supplement). Therefore, COVID-19 was ascertained as a secondary cause from the multiple causes-of-death section, consistent with other reports on excess mortality from COVID-19.4
Deaths were stratified by month, and year of death was stratified into before (2018, 2019, and January-March [quarter 1] 2020) or during (April-December [quarters 2-4] 2020) the pandemic. Maternal mortality rates and percentages with a secondary COVID-19 code were compared by timing, race and ethnicity, and underlying cause (which were all included in NCHS data). Differences were assessed using a z test of proportions. Two-sided P = .05 indicated statistical significance.
A total of 1588 maternal deaths (18.8 per 100 000 live births) occurred before the pandemic vs 684 deaths (25.1 per 100 000 live births) during the pandemic, a relative increase of 33.3% (Table). Late maternal mortality increased by 41%. Absolute and relative changes were highest for Hispanic (8.9 per 100 000 live births and 74.2%, respectively) and non-Hispanic Black (16.8 per 100 000 live births and 40.2%) vs non-Hispanic White (2.9 per 100 000 live births and 17.2%) women (Figure). A secondary code for COVID-19 was listed in 14.9% (102 of 684) of maternal deaths in quarters 2 to 4, with 0% in quarter 1 of 2020. This percentage was highest among Hispanic women (32.1%), followed by non-Hispanic Black (12.9%) and non-Hispanic White (7.3%) women.
For underlying cause-of-death codes (Table), the largest relative increase was among indirect causes (56.9%), specifically other viral diseases (2374.7%), diseases of the respiratory system (117.7%), and diseases of the circulatory system (72.1%). Relative increases in direct causes (27.7%) were mostly associated with diabetes in pregnancy (95.9%), hypertensive disorders (39.0%), and other specified pregnancy-related conditions (48.0%). COVID-19 was commonly listed as a secondary condition with other viral diseases (16 of 16 deaths [100%]) and diseases of the respiratory system (11 of 19 deaths [57.9%]) (Table). Almost half of those with a secondary code for COVID-19 (49 of 102) had a nonspecific code (ICD-10 O26.8 or O99.8) as the underlying cause.
In the US, maternal deaths increased substantially (33.3%) after March 2020, corresponding to COVID-19 onset, a figure higher than the 22% overall excess death estimate associated with the pandemic.4 Increases were highest for Hispanic and non-Hispanic Black women. Change in maternal deaths during the pandemic may involve conditions directly related to COVID-19 (respiratory or viral infection) or conditions exacerbated by COVID-19 or other health care disruptions (diabetes or cardiovascular disease)5 but could not be discerned from the data.
Study limitations include the large percentage of COVID-19 cases with a nonspecific underlying cause (reflecting a maternal death coding problem6) and partitioning of data that resulted in small numbers for some categories (rates were suppressed for <16 deaths). Future studies of maternal death should examine the contribution of the pandemic to racial and ethnic disparities and should identify specific causes of maternal deaths overall and associated with COVID-19.
Published: June 2022