Background A pregnancy question was added to the U.S. standard death certificate in 2003 to improve ascertainment of maternal deaths. The delayed adoption of this question among states led to data incompatibilities, and impeded accurate trend analysis. Our objectives were to develop methods for trend analysis, and to provide an overview of U.S. maternal mortality trends from 2000–2014. Methods This observational study analyzed vital statistics maternal mortality data from all U.S. states in relation to the format and year-of-adoption of the pregnancy question. Correction factors were developed to adjust data from before the standard pregnancy question was adopted, to promote accurate trend analysis. Joinpoint regression was used to analyze trends for groups of states with similar pregnancy questions. Results The estimated maternal mortality rate (per 100,000 live births) for 48 states and Washington D.C. (excluding California and Texas, analyzed separately) increased by 26.6%, from 18.8 in 2000 to 23.8 in 2014. California showed a declining trend, while Texas had a sudden increase in 2011–2012. Analysis of the measurement change suggests that U.S. rates in the early 2000s were higher than previously reported. Discussion Despite the United Nations Millennium Development Goal for a 75% reduction in maternal mortality by 2015, the estimated maternal mortality rate for 48 states and Washington D.C. increased from 2000–2014, while the international trend was in the opposite direction. There is a need to redouble efforts to prevent maternal deaths and improve maternity care for the 4 million U.S. women giving birth each year.

Pregnancy-related mortality should not be considered a single clinical entity. Reducing mortality requires in-depth examination of individual causes of death. The five leading causes exhibit different characteristics, degrees of preventability, and contributing factors, with the greatest improvement opportunities identified for hemorrhage and preeclampsia. These findings provide additional support for hospital, state, and national maternal safety programs.