Limitations of Maternal Mortality Measurement
Worldwide, measuring maternal mortality is difficult because information is needed about pregnancy status at or near the time of death. Autopsy findings may or may not be available.
Some maternal deaths are missed or misclassified. The quality of cause of death information of the death certificate may vary tremendously.
Lack of physician knowledge about the correct way to complete a death certificate is one of the difficulties in correctly measuring the number of maternal deaths.
In other less developed places deaths (and births) just are never recorded.
The World Health Organization states that registered maternal deaths should be adjusted upwards by 50 percent, on average.11
CDC states that the misclassification of deaths underestimates maternal death such that, in the US, the true number of maternal deaths is 1.3 to 3 times higher than reported by vital statistics records.20
Additionally when maternal deaths are relatively rare, they are subject to measurement error.
It has been estimated that more that half of US maternal deaths are not identified through the routine use of cause of death codes on death certificates.
[Pregnancy-Related Mortality in Alabama, December 2005, page 17, by Kathryn L. Chapman, Dr.P.A.
Center for Health Statistics, Division of Statistical Analysis, http://ph.state.al.us/chs/index.htm; http://ph.state.al.us/chs/HealthStatistics/Reports/Pregnancy%20Related%20Mortality.pdf]