Importance of locally derived birth weight nomograms.

Significant differences exist between the published nomograms of birth weight for gestational age. Differences in demographics, altitude above sea level and study methodology have all been implicated. A three-year experience of uncomplicated singleton gestations (N = 14,766) was analyzed for birth weight and gestational age. The mean, 10th percentile and their 95% confidence intervals were compared to Brenner's data and a pooled sample from other studies in this country. The mean birth weights were significantly higher than Brenner's after 32 weeks' gestation and higher than the pooled mean after 35. The 10th percentiles were significantly greater than Brenner's after 36 weeks' gestation. Approximately 66% of neonates at risk, below our 10th percentile, would not be identified with Brenner's criteria. We agree with Goldenberg that uniform criteria for the definition of the normal population are important in identifying aberrant growth. However, birth weight standards should be developed for the specific population in question.