Validation of the global reference for fetal weight and birth weight percentiles

The objective of this study was to evaluate whether the global reference curves adapted on the basis of WHO data for India and the Hadlock reference curves fit the population in India and to validate the reference curves. The data were retrieved retrospectively from the records of women registration for antenatal care at a charitable maternity hospital in Mumbai, India. All pregnancies were dated on CRL obtained before 14 weeks. Births before 34(th) week were excluded. The expected frequencies of birth weights below the 1(st), 5(th), 10(th), 50(th), 90(th), 95(th) and 99(th) centiles from three reference ranges were compared with observed frequencies. It was found that the WHO generic reference adapted to India significantly underpredicted the birth weights and that the Hadlock reference ranges significantly overpredicted the birth weights. The use of generic reference adapted to Sri Lanka showed a better fit to the observed data. We concluded that global reference curves adapted on the basis of WHO data for India and the Hadlock reference ranges do not fit all the population in India and the charts need validation. Reference charts modified on the basis of data for Sri Lankan population show a better fit to the observed data, and therefore are more appropriate for use in clinical practice in South India.