Trends in Mortality Among Pregnant and Recently Pregnant Women in the US, 2015-2019

Abstract

This study uses National Center for Health Statistics data to assess mortality rates and their annual percentage changes for pregnancy-related and other causes among pregnant and recently pregnant women from 2015 to 2019, compared with cause-specific mortality rates in the total US female population of childbearing age.

Maternal mortality involving deaths due to pregnancy-specific causes is higher in the US than in most other developed nations.^1,2 Trends in maternal mortality rates have been challenging to assess because of staggered implementation of the pregnancy checkbox on death certificates between 2003 and 2017,³ although by 2015 all but 2 states (Alabama and West Virginia) had adopted it. Additionally, reports on maternal mortality due to causes of death other than pregnancy are limited. Herein, we report mortality rates and annual percentage changes (APCs) for pregnancy-related and other causes among pregnant and recently pregnant women from 2015 to 2019, and provide a comparison with cause-specific mortality rates within the total female population of childbearing age.

Methods

Deidentified individual-level Multiple Cause of Death files were obtained from the National Center for Health Statistics (2015-2019).⁴ Live birth counts were obtained from the Centers for Disease Control and Prevention’s WONDER database,⁵ as were age-adjusted mortality rates for the total female population of childbearing age. We defined recently pregnant women based on the death certificate pregnancy checkbox³ as either (1) pregnant at time of death or (2) having died within 1 year of the end of pregnancy, consistent with Pregnancy Mortality Surveillance System definitions.⁶ Age groups for death counts, live births, and total female population of childbearing age included standard 10-year groupings (5-14, 15-24, 25-34, 35-44, and 45-54 years; the 5- to 14-year-old group was included because births and deaths occur among girls in the older ages of this grouping). Underlying cause-of-death International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes were used to define causes of death as pregnancy related, drug/alcohol poisoning, motor vehicle collision, homicide, and suicide (eTable in the Supplement). Death counts were summed by year and age group.

Mortality rates per 100 000 were estimated using Poisson regression models, with denominators as live births for recently pregnant women and total female population of childbearing age for the total population, which were weighted to control for age distribution differences. Annual percentage changes in mortality rates were estimated with log-linear regression models. Mortality rates, APCs, and 95% confidence intervals are reported. A 2-sided P<.05 was considered statistically significant. Data were analyzed using R version 4.0.2 (R Core Team). This project was reviewed by the University of Texas at San Antonio Institutional Review Board and determined to be research not involving human subjects.

Results

In total, 9532 recently pregnant women died from 2015 to 2019. The pregnancy-related mortality rate was 27.5 per 100 000 live births in 2019 and was not significantly different from the rate in 2015 (Table 1). Among recently pregnant women, mortality rates per 100 000 live births increased between 2015 and 2019 from 44.4 (n = 1765) to 53.9 (n = 2019) for all causes, from 4.3 (n = 173) to 8.8 (n = 330) for drug/alcohol poisoning, and from 2.0 (n = 79) to 3.9 (n = 148) for homicide. From 2015 to 2019, the increase in mortality rates due to all causes (APC, 4.4%; 95% CI, 2.5%-6.3%) and due to drug/alcohol poisoning (APC, 17.4%; 95% CI, 10.4%-24.4%) were statistically significant, but the increase in mortality due to homicide was not (APC, 13.5%; 95% CI, −2.4% to 29.4%) (Table 1). For the total female population of childbearing age, mortality rates did not increase significantly for any cause. All-cause and drug/alcohol poisoning APCs were statistically significantly higher for recently pregnant women than for the total female population (Table 2).

Table 1. Age-Adjusted All-Cause and Cause-Specific Mortality Rates and Annual Percentage Changes, 2015-2019.

Cause of death	Mortality rate (95% CI)					Annual percentage change (95% CI)	P valuea
	2015	2016	2017	2018	2019
Pregnant or recently pregnant women b
Pregnancy related	26.7 (24.7-28.8)	29.6 (27.4-31.8)	29.3 (27.1-31.5)	24.1 (22.1-26.0)	27.5 (25.4-29.6)	−1.5 (−10.7 to 7.7)	.64
No.	1064	1168	1130	913	1030
Drug/alcohol poisoning	4.3 (3.6-5.1)	5.6 (4.7-6.5)	7.2 (6.1-8.2)	7.8 (6.6-8.9)	8.8 (7.6-10.0)	17.4 (10.4 to 24.4)	.004
No.	173	220	276	294	330
Motor vehicle collision	4.4 (3.7-5.2)	4.3 (3.5-5.0)	4.9 (4.1-5.8)	5.5 (4.6-6.4)	4.6 (3.6-5.3)	2.6 (−8.3 to 13.7)	.51
No.	177	168	190	209	167
Homicide	2.0 (1.5-2.5)	3.2 (2.5-3.9)	3.2 (2.5-3.9)	3.1 (2.4-3.8)	3.9 (3.1-4.8)	13.5 (−2.4 to 29.4)	.07
No.	79	127	124	119	148
Suicide	2.5 (1.9-2.3)	2.5 (1.9-3.2)	2.0 (1.5-2.6)	3.0 (2.2-3.7)	3.1 (2.3-3.8)	5.2 (−10.7 to 21.1)	.38
No.	102	100	79	112	115
All causes	44.4 (41.8-47.0)	48.4 (45.6-51.1)	49.8 (46.9-52.6)	50.7 (47.8-53.6)	53.9 (50.9-56.9)	4.4 (2.5 to 6.3)	.007
No.	1765	1908	1918	1922	2019
Total female population of childbearing age c
Drug/alcohol poisoning	10.7 (10.0-11.5)	13.4 (12.4-14.3)	15 (14.0-16.0)	14.1 (13.2-15.0)	14.2 (13.3-15.1)	6.2 (−4.0 to 16.4)	.15
No.	12 218	14 218	15 572	14 532	14 666
Motor vehicle collision	6.4 (5.8-6.9)	6.9 (6.3-7.6)	6.5 (6.0-7.1)	6.5 (5.9-7.1)	6.4 (5.8-6.9)	−0.6 (−4.1 to 2.9)	.36
No.	6691	7224	6984	6832	6734
Homicide	2.4 (2.1-2.7)	2.7 (2.3-3.1)	2.7 (2.4-3.1)	2.7 (2.4-3.1)	2.6 (2.3-3.0)	1.6 (−3.2 to 6.4)	.40
No.	2511	2833	2901	2871	2797
Suicide	6.2 (5.6-6.9)	6.3 (5.7-7.0)	6.7 (6.0-7.4)	6.8 (6.2-7.5)	6.4 (5.7-7.0)	1.4 (−2.4 to 5.2)	.33
No.	6787	6773	6964	6988	6753
All causes	110.1 (106.9-113.3)	117.9 (114.5-121.2)	119.5 (116.1-122.8)	116.9 (113.6-120.2)	115.4 (112.2-118.7)	0.9 (−2.3 to 4.1)	.47
Total deaths	122 507	125 290	124 232	121 306	119 257

^aP values are based on a t test that the annual percentage change is 0, with 3 degrees of freedom.

^bIncludes 10-year age groups (5-14, 15-24, 25-34, 35-44, and 45-54 years); mortality rates are per 100 000 live births.

^cIncludes 10-year age groups (5-14, 15-24, 25-34, 35-44, and 45-54 years) weighted to live birth age distribution; mortality rates are per 100 000 population.

Table 2. Difference in Annual Percentage Change in Mortality Rates Between Recently Pregnant Women and the Total Female Population of Childbearing Age, 2015-2019, by Cause of Death.

Cause of death	Annual percentage change (95% CI)		Difference (95% CI)	P valuec
	Recently pregnant womena	Total female population of childbearing ageb
All-cause	4.4 (2.5 to 6.3)	0.9 (−2.3 to 4.1)	3.5 (0.6 to 6.4)	.02
Drug/alcohol poisoning	17.4 (10.4 to 24.4)	6.2 (−4.0 to 16.4)	11.2 (1.7 to 20.7)	.03
Motor vehicle collision	2.6 (−8.3 to 13.7)	−0.6 (−4.1 to 2.9)	3.2 (−5.8 to 12.2)	.42
Homicide	13.5 (−2.4 to 29.4)	1.6 (−3.2 to 6.4)	11.9 (−0.7 to 24.5)	.06
Suicide	5.2 (−10.7 to 21.1)	1.4 (−2.4 to 5.2)	3.8 (−8.8 to 16.4)	.49

^aIncludes 10-year age groups (5-14, 15-24, 25-34, 35-44, and 45-54 years); mortality rates are per 100 000 live births.

^bIncludes 10-year age groups (5-14, 15-24, 25-34, 35-44, and 45-54 years) weighted to live birth age distribution; mortality rates are per 100 000 population.

^cP values are based on a t test that the difference in annual percentage change is 0, with 6 degrees of freedom.

Discussion

All-cause mortality rates for recently pregnant women increased 4.4% annually from 2015 to 2019, mostly attributable to causes other than pregnancy-specific complications, including drug/alcohol poisoning, and the APCs for all-cause and drug/alcohol poisoning mortality rates were greater for recently pregnant women than for the total female population of childbearing age.

Limitations include potential misclassification of causes of death and inaccurate pregnancy checkbox documentation, including unknown pregnancy status.³ Additionally, recently pregnant women were contained in the total female population of childbearing age, which suggests that the differences between recently pregnant women and the total female population may be conservative. A 2018 methodology change resulted in fewer deaths among women aged 45 to 54 years being classified as pregnancy related, which could affect the results. However, 94% of these deaths were due to causes other than those assessed in this study.

These findings suggest risk factors beyond pregnancy-specific complications for which enhanced surveillance, prevention, and intervention measures may be warranted. Future studies should include deaths up to 1 year after pregnancy and causes other than pregnancy related.

Section Editors: Jody W. Zylke, MD, Deputy Editor; Kristin Walter, MD, Associate Editor.

Supplement.

eTable. International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) Codes for Each Cause of Death