Predicting significant hyperbilirubinaemia using birth weight.

BACKGROUND: A recent study proposed a risk factor scoring system for prediction of hyperbilirubinaemia that assigned increased risk to infants of higher birth weight. OBJECTIVE: To investigate this novel finding in a large, retrospective cohort analysis. METHODS: 105 384 newborns (> or =2000 g and > or =36 weeks) were analysed, and the effect of higher birth weight on total serum bilirubin (TSB) > or =342 micromol/l was reported using logistic regression to control for gestational age, scalp injury diagnosis, maternal diabetes, method of delivery and other confounders. RESULTS: The odds ratio for the effect of an additional 500 g of birth weight on TSB > or =342 micromol/l declined with increasing gestational age from 1.55 (95% CI 1.28 to 1.87) at 36 weeks to 1.30 (95% CI 1.12 to 1.50) at 37 weeks and 1.14 (95% CI 1.01 to 1.29) at 38 weeks. There was no association for infants > or =39 weeks. CONCLUSION: Higher birth weight predicts TSB > or =342 micromol/l in 36-38 week infants, but not in infants > or =39 weeks. Further research should explore the causal mechanism for the association in less-mature infants.

A meta-analysis of the effect of high weight on asthma.

BACKGROUND: Prevalence rates for both overweight and asthma have been increasing among children in developed countries over the past two decades. Some recent studies have postulated a causal relation between these but have lacked power to form a definitive conclusion. AIM: To estimate the effect of high body weight in childhood on the future risk of asthma. METHODS: Medline search (1966 to October 2004), supplemented by manual search of reference lists and grey literature. Cohort studies that examined high body weight at birth or during childhood and future outcome of asthma were included. Data from each study were extracted on exposure status, clinical outcome, and study characteristics. RESULTS: A total of 402 studies were initially identified, of which 12 met the inclusion criteria. The combined results from four studies that examined the effect of high body weight during middle childhood on the outcome of subsequent asthma showed a 50% increase in relative risk (RR 1.5, 95% CI 1.2 to 1.8). The combined results from nine studies that examined the effect of high birth weight on subsequent asthma had a pooled RR of 1.2 (95% CI 1.1 to 1.3). There was consistency among the results in sensitivity analyses examining studies containing only estimates of odds ratios, studies containing only the outcome of physician diagnosis of asthma, and studies including all definitions of high body weight. CONCLUSIONS: Children with high body weight, either at birth or later in childhood, are at increased risk for future asthma. Potential biological mechanisms include diet, gastro-oesophageal reflux, mechanical effects of obesity, atopy, and hormonal influences. Further research might elucidate the causal pathway, which could improve our understanding of the pathophysiology of asthma and perhaps lead to knowledge of potential preventive interventions.