Objective: To determine the likelihood that infants born to Filipina, other East Asian, and Canadian-born women may be misclassified as small for gestational age when using conventional Canadian birth weight curves rather than those specific to their world region.
Methods: We conducted a population-based study of 548 418 singleton live births in Ontario between 2002 and 2007. Smoothed birth weight percentile curves were generated for males and females born to women from Canada, the Philippines, and the rest of East Asia/Pacific. We determined the likelihood of misclassifying an infant as small for gestational age (SGA < 10th percentile weight) or large for gestational age (LGA ≥ 90th percentile weight) on a Canadian-born birth weight curve vs. a curve specific to the other two world regions.
Results: For gestation-specific 10th and 50th percentiles, term infants born to women from the Philippines often had significantly lower birth weights than infants of Canadian-born mothers. Controlling for maternal age and parity, approximately 88 per 1000 male newborns (95% CI 82 to 95) and 72 per 1000 female newborns (95% CI 54 to 60) of mothers from the Philippines were at risk of being misclassified as SGA. LGA would be missed in approximately 54 per 1000 male newborns (95% CI 49 to 59) and 49 per 1000 female newborns (95% CI 44 to 54) of Filipina mothers. Misclassification of both SGA and LGA was more pronounced among infants of Filipina mothers than of mothers from other East Asian origin.
Conclusions: Infants of mothers born in the Philippines weigh significantly less than those of Canadian-born women or mothers emigrating from other East Asian countries. Those who use birth weight curves should consider these differences.