UBC study challenges alarming U.S. maternal death rate reports

Science, Health & Technology

Reports of a dramatic upward trend in the U.S. maternal death rate are being challenged by new UBC research published today in the American Journal of Obstetrics and Gynecology.

“Our study showed that maternal mortality rates were low and stable between 1999-2002 and 2018-2021, which is very different from the high rates and dramatic increases reported by the National Vital Statistics System in recent years,” said lead author Dr. K.S. Joseph, a professor in the department of obstetrics and gynaecology and school of population and public health at UBC, and investigator at the BC Children’s Hospital Research Institute.

Maternal deaths refer to those occurring during pregnancy, childbirth, or the post-partum period from conditions directly related to pregnancy or those exacerbated by pregnancy and birth. Accidental and incidental deaths in pregnancy are not included in the definition of maternal death.

Recent estimates from the National Vital Statistics System show that maternal death rates in the U.S. nearly doubled from 2018 to 2021, but doubts have lingered regarding the accuracy of the reports.

Dr. Joseph and a team of international researchers took a deep dive into the underlying data and looked at factors that could be driving the purported increase: changes in obstetric factors, maternal chronic conditions and changes in data collection methods. They examined all deaths in the U.S. between 1999 and 2021 using an approach that enables greater accuracy in how maternal deaths are identified and classified in the mortality database.

The study uncovered several indications that a pregnancy checkbox introduced on death certificates in 2003 to indicate the death of a pregnant person was responsible for misclassifying non-maternal and incidental deaths during pregnancy as maternal deaths.

The research group’s approach was to identify maternal deaths by requiring mention of pregnancy among the multiple causes of death. This revealed stable maternal mortality rates and declines in maternal deaths from direct obstetric causes.

“We found that exclusive reliance on the pregnancy checkbox on death certificates, without corroboration from the cause-of-death information, led to an overestimation of maternal mortality rates by the NVSS in 2018-21,” said Dr. Joseph.

The pregnancy checkbox’s use between 2003 and 2017 was associated with some substantial errors. A detailed investigation by the National Center for Health Statistics (NCHS) showed that the checkbox was erroneously ticked in many cases, leading to misclassification and overestimation of maternal death. For example, hundreds of people 70 years of age and older (including 147 women aged 85 years and older in 2013) were certified as pregnant at the time of death or in the year prior. The NCHS concluded that the entire increase in maternal mortality in the U.S. between 2003 and 2017 was due to the pregnancy checkbox. In response, NCHS made specific changes regarding pregnancy checkbox use for deaths from 2018 onwards, but NVSS reports showed that maternal mortality rates continued to rise.

“By not relying on the pregnancy checkbox, our approach avoided the misclassification that has given the false impression of increasing maternal mortality rates in the U.S.,” said co-author Dr. Justin S. Brandt of the department of obstetrics and gynecology at NYU Grossman School of Medicine.

The study showed a reduction in overall maternal mortality, and especially in maternal deaths from direct obstetric causes among non-Hispanic Black Americans. However, it also revealed persistent racial and ethnic disparities, including disproportionately high rates of maternal death among non-Hispanic Black Americans.

“The persistent racial and ethnic disparities we see in maternal mortality, including the high rates among people who are Black and the temporal increase among white Americans, are extremely concerning and need to be addressed,” said Dr. Sarka Lisonkova, associate professor in the department of obstetrics and gynaecology at UBC, and investigator at the BC Children’s Hospital Research Institute. “Our findings also emphasize the importance of accurate data collection regarding disparities in maternal mortality, not only within the United States but also in Canada.”

The study provides important insights into cause- and race/ethnicity-specific maternal mortality and provides suggestions for the appropriate use of the pregnancy checkbox on death certificates. The authors hope the findings will serve as the evidentiary basis for clinical and public health initiatives for reducing maternal mortality.