Women’s Health
Temporal Trends in Maternal Mortality in Canada I: Estimates Based on Vital Statistics Data

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Abstract

Objectives

Vital Statistics and World Health Organization reports show a recent increase in maternal mortality in Canada. We carried out a study of temporal trends, regional variations, and causes of death in Canadian maternal mortality using Vital Statistics data.

Methods

We used Vital Statistics death registrations to ascertain maternal deaths between 1981 and 2007. Maternal mortality rates, risk ratios, and 95% confidence intervals were estimated, and the Cochran-Armitage test was used to evaluate temporal trends. We used hospitalization data from the Canadian Institute for Health Information from 1996 to 2007 to confirm maternal mortality trends observed in the Vital Statistics data.

Results

Maternal mortality rates increased significantly from 4.5 (95% CI 3.3 to 5.8) in 1981 to 1983 to 4.7 (95% CI 3.5 to 6.2) in 1996 to 1998 and to 7.2 (95% CI 5.7 to 9.0) per 100 000 live births in 2005 to 2007 (P value for trend < 0.001). The most common causes of maternal death were diseases of the circulatory system, obstetric embolism (venous thromboembolism and amniotic fluid embolism), and hypertension. Deaths due to diseases of the circulatory system and puerperal infection increased significantly from 1981 to 2007. Maternal mortality rates in the hospitalization data were higher and did not show an increase over time. Provincial and territorial maternal mortality rates from Vital Statistics data showed varying degrees of under-ascertainment (12% to 70%) compared with hospitalization data.

Conclusion

Temporal increases in maternal mortality in Canada observed in Vital Statistics data do not correspond with stable temporal trends observed in hospitalization data, and appear to be an artefact of changes in the coding and ascertainment of maternal deaths.

Résumé

Objectifs

Des rapports du Bureau de l’état civil et de l’Organisation mondiale de la santé indiquent une récente hausse de la mortalité maternelle au Canada. Nous avons mené une étude des tendances temporelles, des variations régionales et des causes de décès en matière de mortalité maternelle au Canada au moyen de données issues du Bureau de l’état civil.

Méthodes

Nous avons utilisé les enregistrements de décès du Bureau de l’état civil pour déterminer les décès maternels entre 1981 et 2007. Les taux de mortalité maternelle, les risques relatifs et les intervalles de confiance à 95% ont été estimés, et nous avons eu recours au test de Cochran-Armitage pour évaluer les tendances temporelles. Nous avons utilisé les données d’hospitalisation émises par l’Institut canadien d’information sur la santé entre 1996 et 2007 pour confirmer les tendances de mortalité maternelle constatées dans les données du Bureau de l’état civil.

Résultats

Les taux de mortalité maternelle ont connu une hausse significative en passant de 4,5 (IC à 95 %, 3,3 – 5,8) pour la période 1981 - 1983 à 4,7 (IC à 95 %, 3,5 – 6,2) pour la période 1996 - 1998 et à 7,2 (IC à 95 %, 5,7 – 9,0) par 100 000 naissances vivantes pour la période 2005 - 2007 (valeur P pour la tendance < 0,001). Les causes les plus courantes de décès maternel étaient les maladies du système circulatoire, l’embolie obstétricale (thromboembolie veineuse et embolie du liquide amniotique) et l’hypertension. Les décès attribuables aux maladies du système circulatoire et à l’infection puerpérale ont connu une hausse significative entre 1981 et 2007. Les taux de mortalité maternelle dérivés des données d’hospitalisation étaient plus élevés et ne connaissaient pas de hausse avec le temps. Les taux provinciaux et territoriaux de mortalité maternelle dérivés des données du Bureau de l’état civil indiquaient divers degrés de sous-détermination (de 12 % à 70 %), par comparaison avec les données d’hospitalisation.

Conclusion

Les hausses temporelles des taux de mortalité maternelle au Canada que permettent de constater les données du Bureau de l’état civil ne correspondent pas avec les tendances temporelles stables que permettent de constater les données d’hospitalisation et semblent constituer un artéfact des modifications du codage et de la détermination des décès maternels.

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    Competing Interests: None declared.

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