Abstract
Background: The classification of small for gestation age (SGA) is defined as birth weight below the 10th percentile on growth charts. A commonly used growth chart, Lubchenco (Pediatrics, 1969), was developed in the1960's, but concerns have been raised about its validity due to its use of population at high altitude and the exclusion of racial/ethnic minorities. SGA is associated with infant morbidity and mortality and may be associated with adult-onset disease, the “metabolic syndrome.” the utilization of the traditional growth curve may underestimate the number of children who are born SGA and who have additional neonatal morbidities and increased risk of life-long chronic disease.
Objective: To compare the 10th percentile birth weights in a Kansas City newborn sample using the Lubchenco growth curve compared to a curve generated by a local population data.
Design/Methods: Retrospective cohort study of births at Truman Medical Center in Kansas City, Missouri. The birth records of 5,687 sequential births were assessed to obtain gestational age based on maternal data (last menstrual period or prenatal ultrasound) and birth measurements. Outcome of interest was SGA. The 10th, 50th and 90th percentiles for each gestational age were calculated. Deviations from the Lubchecno growth curves were calculated for each gestational age. The proportion of SGA in the Kansas City cohort, as defined by the Lubchenco chart, was also computed.
Results: For infants with gestational age of 32 weeks and above, the Kansas City cohort had substantially larger values for the 10th percentile. The average deviation was 9% (range: 4% to 16%). The proportion of the Kansas City cohort that would be classified as SGA by the Lubchenco growth curve would only be 5%, less than half of the expected value (95% confidence interval 4.5% to 5.6%).
Conclusion: A significant number of infants born after 32 weeks gestation are SGA when plotted on locally-generated growth curves compared to the Lubchenco growth curves. It is apparent that the commonly used Lubchenco growth curves may not be appropriate for recognizing SGA in our population. Future investigations will determine whether or not the newborns whose diagnosis has been missed by the use of the Lubchenco charts suffer the morbidity and mortality associated with SGA.
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Fitzgerald, K., Pettett, G., Okah, F. et al. 17 Traditional Growth Curve Compared with Contemporary Local Curve Fails to Identify SGA Infants.. Pediatr Res 58, 819 (2005). https://doi.org/10.1203/00006450-200510000-00047
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DOI: https://doi.org/10.1203/00006450-200510000-00047