Trends in low birthweight Canada. 1971 to 1989.

This paper reviews the levels of and the trends in low birthweight (under 2,500 grams) and premature births (less than 37 weeks gestation) in Canada from 1971 to 1989. Low birthweight (LBW) characterized 6.6% of births in 1971 and 4.6% of births in 1989: this represents a decline of 30% in LBW for the period. The decline was evident for mothers in all age groups, and for all birth parities. However, the prevalence of very low birthweights (less than 1,500 g) remained stable during the period, accounting for 0.8% of births in 1971 and 0.7% in 1989. Preterm births (less than 37 weeks of gestation) increased from 47% of all LBW births in 1971 to 60% in 1989. This shift and the small decline in the prevalence of preterm LBW babies has clinical and preventive implications. These and other findings are based on analysis of 6.6 million single live births between 1971 and 1989.