A new analysis of maternal mortality worldwide conducted by the United Nations found that the maternal mortality ratio saw a relative decline of 43.9 percent during the 25-year period of 1990-2015. Details appear in an early online issue of The Lancet.

The study analyzed levels and trends in maternal mortality in 183 countries and found that the maternal mortality ratio declined from 385 deaths per 100,000 live births in 1990 to 216 in 2015. They also saw great variability in progress toward reducing mortality. 

Estimation of maternal mortality and associated uncertainty is challenging for many countries due to data issues: data availability is limited for many countries and the uncertainty associated with available data tends to be substantial due to measurement issues.

While past efforts in constructing estimates had focused on using covariates such as gross domestic product, fertility rates and presence of skilled birth attendants to produce trend estimates for countries with limited data, that approach was no longer satisfactory for countries where more data had become available, especially in recent years. 

Statisticians spent over a year developing a Bayesian estimation model used in the study. This model built onto the covariate-based approach used in earlier years, but extended it to better capture trends and recent levels of maternal mortality at the country-level, and to take into account the variable quality of observations, she says. 

The authors report observing the greatest relative reduction in Eastern Asia, where the maternal mortality ratio fell from approximately 95 to 27 per 100,000 live births, a reduction of 72 percent, but it was lower in all other regions. Globally, the rate of change fell short of the progress envisioned under the UN's 5th Millennium Development Goal, which called for a reduction in 75 percent between 1990 and 2015, the authors report.

At the country level, nine countries did achieve a 75 percent reduction in 25 years, the researchers say, noting that successful interventions in these countries can help to guide action and global progress in future years.