Birthweight standards - Ability of birthweight percentiles in predicting abnormal fetal growth and outcome

Abstract

Introduction: Birthweight references for different populations are varied and most of abnormal growth deviations of given populations could be detected by creating local birthweight charts. The aim of this study was to compare the accuracy of commonly used birthweight centile charts in birthweight percentiles in predicting abnormal growth trajectories. Methods: This was a retrospective analytical study conducted between April 2010 and October 2013. Patient data and mortality data were traced from respective units and cross checked with the hospital monthly perinatal statistics. Centile values of >90th (large for gestational age -LGA),10th - 90th (appropriate for gestational age -AGA) and <10th (small for gestational age - SGA) of previously validated Sri Lankan fetal/ birthweight charts were compared with birthweight charts adopted by child health development record (CHDR) and for commonly used Hadlock charts. Proportions of adverse outcomes (perinatal deaths and late neonatal deaths) among preterm (<37 weeks) and term deliveries were also compared for SGA, AGA and LGA in three different birthweight centile charts. Results: Among 12501 singleton births, preterm and term neonates were classified differently for SGA, AGA, and LGA by Sri Lankan, CHDR and Hadlock birthweight references. More than 20% of babies were SGA by CHDR charts. SGA derived from Sri Lankan charts have detected significantly higher proportion of adverse outcomes among preterm babies than Hadlock (OR 2.08 95% CI, 1.21 to 3.56) charts. Furthermore, there is a positive trend in detecting more adverse outcomes among SGA babies from Sri Lankan charts than CHRD and Hadlock charts at term (OR 1.44, 95% CI, 0.66 to 3.12 and OR 1.93, 95% CI, 0.98 to 3.82 respectively). Conclusions: The newly created Sri Lankan birthweight chart detects most true SGA infants. It also improves the classification of abnormalities in birthweight and predicts substantially higher adverse outcomes. These new reference charts are clinically effective and can be used in the Sri Lankan population. DOI: http://dx.doi.org/10.4038/sljog.v36i4.7729 Sri Lanka Journal of Obstetrics and Gynaecology Vol.36(4) 2014: 85-88 Keywords: Birth weight standards, Fetal growth abnormalities, Prediction, Adverse perinatal outcome, Patient care, Preventive medicine