Changes in the registration of stillbirths < 500 g in Canada, 1985–95

We assessed recent temporal trends in the registration of stillbirths in Canada, with particular regard to stillbirths < 500 g. Data from the Statistics Canada live birth and stillbirth databases for the period 1985-95 were used for the study. The primary analysis was restricted to data from 10 of the 12 provinces and territories of Canada. Data from Newfoundland were excluded because birthweight distributions were not available prior to 1990, and data from Ontario were excluded because of concerns about data quality. The proportion of stillbirths < 500 g increased by 47% [95% confidence interval (CI) 32, 63%], from 12.7% of stillbirths with known birthweight in 1985-7 to 18.7% in 1993-5. Similarly, the rate of stillbirths < 500 g increased by 36% [95% CI 21, 53%], from 7.2 to 9.8 per 10,000 total births from 1985-7 to 1993-5. Similar increases in stillbirth rates were not observed in other low birthweight categories. Live births < 500 g increased 53% [95% CI 33, 77%], from 4.6 to 7.0 per 10,000 live births. Some provinces and territories had low rates of stillbirths < 500 g and no increasing trend, whereas other provinces showed higher rates and increases over time. These regional differences were consistent with differences in stillbirth definitions across the provinces and territories of Canada. Spatio-temporal comparisons of crude stillbirth rates are likely to be compromised unless differences and changes in birth registration practices are addressed.