{"doi":"10.1111/ppe.13139","title":"Making sense of US maternal mortality data","abstract":"Accurately identifying US maternal deaths has significant challenges. Data is collected and measures reported independently by two different national organisations and over 50 different state and local jurisdictions. There are at least two different definitions widely used: WHO Maternal Mortality Rate, used by the National Center for Health Statistics, limits deaths during or up to 42 days post-end of pregnancy and the CDC Pregnancy-Related Mortality Rate also used by state maternal mortality committees that include deaths up to a year after the end of the pregnancy. The very low rate of maternal deaths in both measures makes them especially sensitive to changes in definition and user error in the completion of vital records. The article by Joseph and colleagues, ‘Maternal mortality in the United States: are the high and rising rates due to changes in obstetrical factors, maternal medical conditions, or maternal mortality surveillance?’, discusses the consequences of these issues in detail.1 Here we provide some additional insights into the difficulties and successes of measuring maternal deaths. Measuring maternal mortality is altogether different from measuring infant mortality. Very limited data is required for generating infant mortality rate including the date of death, the date of birth and the gestational age (to allow for cut-offs at either 20 or 28 weeks). Minimal or no judgements are needed. The definition has remained unchanged for generations. In contrast, accurate assessment of maternal deaths requires multiple data sources and a series of judgements. First, we need to identify deaths among all pregnant persons and persons who delivered in the prior 42 days, and even more difficult, persons who delivered in the last year following the end of a pregnancy. Even the linkage of all death records to birth records (which can lead to significant delays) will miss maternal deaths that occurred before 20 weeks of gestation. But the hardest judgement is determining, without review of the medical records, whether the death from a medical cause was ‘related to or aggravated by the pregnancy.’ Even in a maternal mortality review committee with access to autopsy results and full case records, it can still be a very subjective and hotly debated decision. To make matters even worse, the maternal mortality definitions and even the fields on the death certificate have changed multiple times in the last 40 years.2 Our current challenges are directly related to these issues. An oft taught rule in public health is that an abrupt large change in population outcomes is usually associated with a change in either data collection or measure definition. The change from ICD-9 to ICD-10 for Death Certificates in 1999 is a case in point. Under ICD-9 rules, a death could only be counted as pregnancy-related if pregnancy was identified in the list of immediate and underlying causes (US Death Certificate Part 1). Under ICD-10, the definition of pregnancy-related death was expanded to additionally include deaths where pregnancy was noted as ‘conditions that contributed to death but was not part of the chain of events that led directly to death’ (US Death Certificate Part 2).2 The inclusion of these deaths where the pregnancy was not on ‘the casual pathway’ led to an immediate and significant increase in the rate of maternal deaths from ‘primarily medical causes’ (indirect deaths) from 1.8 to 8.1 per 100,000. However, not often acknowledged, the actual rate of ‘primarily obstetric causes’ has remained fixed at 7.9 per 100,000 (Table 1).3 Multiple authors have also noted the steady increase in the rates of maternal comorbidities which has also contributed to the rising rates of severe maternal morbidity and maternal deaths due to ‘primarily medical causes’.1, 4, 5 In this same time period, public health leaders were concerned about underreporting of maternal deaths because of lack of recognition of pregnancy on the death certificate. As many as 30%–","journal":"Paediatric and Perinatal Epidemiology","year":2024,"id":477932,"datarank":0.2302557436864335,"base_score":1.0986122886681096,"endowment":1.0986122886681096,"self_citation_contribution":0.16479184330021646,"citation_network_contribution":0.06546390038621705,"self_endowment_contribution":0.16479184330021646,"citer_contribution":0.06546390038621705,"corpus_percentile":38.09081766844589,"corpus_rank":8003,"citation_count":2,"citer_count":2,"citers_with_citation_signal":1,"citers_with_endowment":1,"datacite_reuse_total":0,"is_dataset":true,"is_dataset_confidence":0.669,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2024-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":680270,"name":"Elliott K. Main","orcid":"0000-0001-7562-7850","position":0,"is_corresponding":true}],"reference_count":10,"raw_metadata":null,"created_at":"2026-07-19T02:06:37.812633Z","pmid":"39529402","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}