Taiwan birth weight reference.

Topçu et al are the authors of a good reference article entitled “Birth weight for gestational age: a reference study in a tertiary referral hospital in the middle region of Turkey”. This retrospective study enrolled 68,255 live singleton pregnancies delivered at 22e42 gestational weeks in Dr Zekai Tahir Burak Women's Health Education and Research Hospital, Ankara, Turkey, between 2007 and 2013. Although we applaud the publication of this article, the underlying study added little new information to the existing literature. Several population-based references for measuring birth weight for gestational age have been previously generated. However, most of these studies focused on Western countries. For example, a recent publication by Talge et al used an algorithm based on birth weight and the concordance between these gestational age estimates to calculate the gestational ageand sex-specific birth weight means, standard deviation (SD), and smoothed percentiles (3, 5, 10, 90, 95, and 97) by the National Center for Health Statistics (n 1⁄4 8,130,051 births to United States resident women). The main findings of Talge et al's study included (1) nearly 90% of births occurred at term (37e41 weeks), whereas 8% and 2% of births occurred within the preterm (<37 weeks) and postterm ranges ( 42 weeks), respectively; (2) males comprised 51% of the births, and 49% of infants were first-borns; (3) non-Hispanic white was the most prevalent (54%); (4) the mean gestational age at delivery was 38.6 weeks with a SD of 2 weeks; (5) birth weight increased as gestational week increased, with the largest SDs observed after 33 weeks for both males and females; and (6) the 50 percentile of body weight at 38 weeks, 39 weeks, and 40 weeks was 3183 g, 3315 g, and 3407 g, respectively (Table 1). By contrast, Topçu et al's study provided significantly less information, including (1) the 50 percentile of body weight at 38 weeks, 39 weeks, and 40 weeks was 3220 g, 3320 g, and 3400 g, respectively; and (2) males comprised 54.1% of the births, even though investigators claimed that their study was the first to evaluate such a number of participants in Turkey and the results might be a good reference to define normal and abnormal fetal growth in newborns in Turkey. In addition, as shown by Topçu et al, this study was based on cross-sectional data; therefore, it does not reflect the longitudinal growth trajectory of individual infants. It is possible that longitudinal assessments of fetal size, although more expensive and challenging to obtain, might yield estimates that diverge from those