Monitoring progress in reducing maternal mortality using verbal autopsy methods in vital registration systems: what can we conclude about specific causes of maternal death?

The World Health Organization recommends the use of verbal autopsy (VA) methods to measure maternal mortality in countries without adequate medical certification of the cause of death, in part to enable them to monitor progress towards the Sustainable Development Goal of reducing the global maternal mortality ratio to less than 70 per 100,000 live births [1, 2]. This recommendation implies that procedures for the collection of VAs are in place to ensure the completeness of reporting of maternal deaths and that sufficient information about the cause of each maternal death from these sources is available to guide policy responses.

VAs were developed in Demographic Surveillance Sites in the 1980s and 1990s to identify leading causes of death in populations where the coverage of medical certification was limited [3]. The method was subsequently used for the assignment of cause of death for specific diseases for research purposes [4]. Over the last 4 years, the Bloomberg Data for Health Initiative to strengthen civil registration and vital statistics (CRVS) systems in low- and middle-income countries has facilitated the routine application of VAs in vital statistics systems to generate cause of death data for hitherto underserved populations [5]. Currently, VA questionnaires have been shortened, with less emphasis on open-ended responses due to inter-interview variability [6]. VA interviewers are commonly recruited from health services, with the collection of VAs representing an additional task.

Our experience assembled under the Bloomberg Data for Health Initiative over the past 4 years is that VAs collected through CRVS are sufficient to identify the leading 10–20 causes of death in low- and middle-income countries, including maternal deaths [5]. However, we argue that routine application of VAs in CRVS systems is not sufficient to obtain the necessary detailed information about the specific causes of maternal death that the World Health Organization 2016 VA Instrument aims to identify (Box 1) [7]. While it would clearly be desirable to be able to generate such epidemiological specificity from routine application of VAs in a CRVS system, we do not believe that these data can be collected with sufficient accuracy to be useful for public policy. Rather, we suggest that, in order to reliably describe the distribution of maternal causes in a population using VAs, a two-step process is required, involving (1) the identification of a maternal death using VAs and (2) the collection of detailed data by dedicated interviewers in a follow-up enquiry involving family and community collaboration.

Any death, and particularly a maternal death, is an emotional event for the family and relatives, but reporting and correctly diagnosing it is an important first step in providing the necessary health intelligence to guide health system responses. Our field experience regarding the ability of a VA interview and automated diagnostic algorithm to reliably distinguish between specific causes of maternal death, along with our interpretation of the very limited evidence, suggests that countries should be very cautious when assuming that VA methods designed for routine application are, inherently, sufficiently reliable to do so. All risk factors being equal, maternal mortality is highest for unsupervised deliveries [14]. Home deliveries often take place under adverse conditions and, when a woman is dying, panic may ensue. In such circumstances, it is unlikely that a (female) respondent to a VA interview will accurately recall, or even identify, some of the key symptoms required to adequately discriminate among maternal causes [15]. This would be even less likely if the VA respondent was a male who may or may not have been present when the events unfolded. Rather, accurate information about the causes of maternal death requires the development of a cadre of specially trained interviewers, the selection of one or more well-informed respondents, and careful, sympathetic questioning. Using VA to identify the causes of maternal deaths will be strengthened by the addition of separate semi-structured interviews focusing not only on the family, but also on health workers familiar with the details of the pregnancy. This is not current practice in countries trialing the routine application of VA in CRVS systems. Increasingly complex questionnaires and computer algorithms based on physician opinion will not solve the problem. Rather, we strongly recommend a two-step process of identifying deaths during routine CRVS followed by a detailed maternal mortality inquiry/survey. This paired, sequential approach to identifying the distribution of specific causes of maternal deaths will likely provide much more reliable evidence to better inform policy responses in countries as they strive to achieve the Sustainable Development Goal of reducing maternal mortality than data collected through VAs alone.