Fetal size classified using gestational days rather than gestational weeks improves correlation with stillbirth risk: A statewide population study.

Growth standards using a single cutoff for a gestational week overestimate the proportion of infants that are small at the beginning of the week and underestimate the proportion at the end. This distorts the risk of stillbirth amongst SGA infants based on when in the week an infant is born. Day-based charts should be used.