Global, Regional, and National Trends in Maternal Mortality Ratio Across 37 High Income Countries From 1990 to 2021, With Projections up to 2050: A Comprehensive Analysis From the WHO Mortality Database

Abstract

Background: Understanding the global trends and future projections of maternal mortality ratio (MMR) is crucial as it can provide insights into improving policies and healthcare systems aimed at enhancing the quality of obstetric care and reducing preventable deaths. Given recent reports of increasing MMR trends in some high-income countries (HICs), we aimed to analyze the global trends of MMR from 1990 to 2021 and project future trends until 2050 across 37 countries.

Methods: Age-standardized country-specific MMR for 37 countries from 1990 to 2021 were assessed through a locally weighted scatter plot smoother (LOESS) curve, with weighting based on individual country populations, utilizing the World Health Organization Mortality Database. The impact of premature mortality due to MMR was assessed by analyzing the years of life lost (YLLs). Furthermore, projections for MMR up to 2050 were derived using the Bayesian Age-Period-Cohort (BAPC) model. Decomposition analysis identified factors contributing to MMR variations such as population growth, aging and epidemiological changes.

Results: The LOESS estimate of the global MMR decreased from 25.65 deaths per 100,000 live births (95% confidence interval [CI], 22.10, 29.20) in 1990 to 10.38 (6.41, 14.36) in 2021. While most continents showed a decreasing trend, young age groups in Asia-Pacific regions and all age groups in North America exhibited no significant changes from 1990 to 2021. MMR due to direct causes declined from 25.05 deaths per 100,000 live births (95% CI, 21.71, 28.38) in 1990 to 7.66 (3.90, 11.43) in 2021 across all age groups. Conversely, MMR due to indirect causes rose from 0.33 deaths per 100,000 live births (95% CI, -0.37, 1.03) in 1990 to 4.33 (3.43, 5.23) in 2021, with a more pronounced increase in advanced age groups. YLL due to MMR decreased from 866.00 (95% CI, 692.39, 1,039.60) in 1990 to 387.05 (182.82, 591.28) in 2021. Our analysis revealed negative correlations between MMR and the Human Development Index, Socio-demographic Index, and Universal Health Coverage Service Index. BAPC models predict a continued decrease in global MMR to 4.47 (4.07, 4.89) in 2030, 2.32 (1.82, 2.89) in 2040, and 1.25 (0.86, 1.81) in 2050. However, MMR due to indirect causes is projected to consistently increase. The global decrease in MMR from 1990 to 2021 can be primarily attributed to epidemiological changes.

Conclusion: This study reveals a significant global decline in MMR since 1990, with projections indicating further decreases up to 2050, despite persistent increases in indirect causes and mortality among older age groups. These findings highlight the critical need for targeted strategies to address indirect causes and protect vulnerable populations.

Keywords: Global Trend; Maternal Mortality Ratio; Prediction Model; WHO Mortality Database.

Fig. 1. Age-standardized maternal mortality ratio attributed to all causes, direct causes, and indirect causes for the global population among 37 countries for the years 1990–2021. The LOESS mortality rates with 95% confidence levels are shown in red.

LOESS = locally weighted scatter plot smoother.

Fig. 2. Age-standardized all causes of MMR across 37 countries for the global and populations across four continents, 1990–2021. The LOESS mortality rates with 95% confidence levels are shown in red. Asia Pacific includes 8 countries, including Australia, Brunei Darussalam, Hong Kong SAR, Israel, Japan, New Zealand, the Republic of Korea, and Singapore. Europe includes 21 countries, including Austria, Belgium, Croatia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Netherlands, Poland, Portugal, Romania, Slovenia, Spain, Sweden, Switzerland, and the United Kingdom. Latin America and the Caribbean include 6 countries, including Bahamas, Chile, Panama, Puerto Rico, Trinidad and Tobago, and Uruguay. North America includes 2 countries, including Canada and the United States of America.

MMR = maternal mortality ratio, LOESS = locally weighted scatter plot smoother.

Fig. 3. LOESS smoothed MMR attributed to all causes, direct causes, and indirect causes by sex and age group among 37 countries, 1990–2021.

MMR = maternal mortality ratio, LOESS = locally weighted scatter plot smoother.

Fig. 4. Correlation between age-standardized all causes MMR and human development index, socio-demographic index, UHC service index, and Gini coefficient.

MMR = maternal mortality ratio, UHC = Universal Health Coverage.

Fig. 5. Projections in age-standardized MMR attributed to all causes, direct causes, and indirect causes from 2022 to 2050 by Bayesian age-period-cohort models. (A) Represents all causes of MMR, (B) denotes direct causes of MMR, and (C) signifies indirect causes of MMR.

MMR = maternal mortality ratio.

Fig. 6. Changes in the number of maternal deaths attributed to all causes, direct causes, and indirect causes associated with aging, epidemiological change, and population from 1990 to 2021 and 1990 to 2050.