[Birthweight curves: a review of the literature]

There are many birthweight reference curves in the literature. This study reviews birthweight curves that are commonly used in France as well as references that provide birthweight by sex. The 19 curves selected for review were published between 1971 and 2001 using samples of between 300 to 3 million newborns in Europe, Australia and North America. Our objective was to summarize their main characteristics and to provide guidelines for analysis by explaining which factors are responsible for differences between curves, and discussing the methods used to construct them. The characteristics of the population must be taken into account and study samples must be recent and representative. The sample size must be sufficient to ensure stable estimates for premature infants. It is preferable to use different curves for boys and girls because sex is a key determinant of birth weight. The choice of appropriate birth weight reference remains difficult in some countries, in France particularly, and the use of individual customised birth weight curves provides an interesting alternative.