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

We assessed recent temporal trends in the registration of stillbirths in Ca nada, with particular regard to stillbirths < 500 g. Data from the Statisti cs Canada live birth and stillbirth databases for the period 1985-95 were u sed for the study. The primary analysis was restricted to data from 10 of t he 12 provinces and territories of Canada. Data from Newfoundland were excl uded because birthweight distributions were not available prior to 1990, an d data from Ontario were excluded because of concerns about data quality. T he proportion of stillbirths < 500 g increased by 47% [95% confidence inter val (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 ot her low birthweight categories. Live births < 500 g increased 53% [95% CI 3 3, 77%], from 4.6 to 7.0 per 10 000 live births. Some provinces and territo ries 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 acr oss 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.