Figure 1From: Temporal trends in the frequency of twins and higher-order multiple births in Canada and the United States Temporal trends in rates of twin live births (upper panel) and triplet and higher-order (triplet+) multiple live births (lower panel) in Canada (excluding Ontario), and the United States, 1991–2009. Plots depict observed rates of twins (per 1,000 live births) and 3-year moving averages of observed rates for triplet+ (per 100,000 live births).Back to article page