Seven caveats on the use of low birthweight and related indicators in health research.

Birthweight and gestational age are the two most commonly used continuous variables in perinatal research. Dichotomous outcomes derived from these two variables include low birthweight, preterm birth and small for gestational age, each extensively used as perinatal and population health indicators within public health research and health surveillance systems. However, these dichotomous indicators have inherent limitations that need to be considered in the design, analysis and interpretation of epidemiological studies. In this report, we present seven caveats that may help researchers and users of epidemiological data avoid common (and not so common) pitfalls in the consideration of these indicators.