Severe maternal morbidity in Canada, 2003 to 2007: surveillance using routine hospitalization data and ICD-10CA codes

To examine the feasibility of using routine labour and delivery hospitalization data and international classification of diseases (ICD-10CA) codes for carrying out surveillance of severe maternal morbidity in Canada.

We identified ICD-10CA diagnosis codes and Canadian Classification of Interventions (CCI) procedure codes associated with severe maternal illness. Severe maternal morbidity rates in Canada (excluding Quebec) for the period 2003 to 2007 were estimated using the Discharge Abstract Database of the Canadian Institute for Health Information. Rates were compared across maternal age, parity, plurality, labour induction, delivery by Caesarean section, and other factors. Case fatality rates and length of hospitalization were also estimated.

Among the 1 336 356 women who delivered between 2003 and 2007, the rate of severe maternal morbidity was 13.8 per 1000 deliveries. The mean length of hospital stay for women with and without a severe illness was 5.4 days vs. 2.5 days, while the frequency of prolonged hospital stay (>or=7 days) was 19.8% vs. 1.8%, respectively (rate ratio 9.3; 95% CI 9.0 to 9.6). Case fatality rates differed significantly between women with and without a severe illness at 2.98 vs. 0.008 per 1000, respectively (rate ratio 392.8; 95% CI 200.3 to 700.4). Rates of severe maternal morbidity were higher among deliveries to older and nulliparous women and to those delivering twins or triplets.

Disease frequency, case fatality, and length of hospitalization patterns suggest that comprehensive and timely surveillance of severe maternal morbidity in Canada is feasible using the Canadian Institute for Health Information hospitalization data and ICD-10CA/CCI codes.