For countries / populations where there is insufficient data on maternal and pregnancy characteristics, we can provide a tool GRAW(Gestation Related Average Weight) into which a population average birthweight at term can be entered. From this unadjusted term weight, the corresponding weight at each gestational age is calculated through the proportionality growth formula [1]. The normal range, represented by the 10th and 90th centile limits, is calculated by adding or substracting 14% of the median weight at each gestation [1]. Once the average term weight of the local population is entered, the GRAW chart can then be printed out and used for antenatal care. As an example, a chart for Bangladesh, based on a term average weight at 40.0 weeks of 2955g, is available here.

Retrospectively, birthweight centiles based on the local population average birthweight can also be calculated, by entering the gestational age at delivery, birthweight, and, optionally, the sex of the baby.

Reference: [1] Gardosi J, Mongelli M, Wilcox M, Chang A. An adjustable Fetal Weight Standard. Ultrasound Obstet Gynecol 6 (1995);168–174.

Disclaimer: Our software use formulae containing calculations made on the basis of published principles and formulae. The authors cannot accept responsibility for any clinical diagnoses or decisions made on the basis of this software.