[Recommendations for the assessment of birth size and postnatal growth of preterm newborns].

It is unquestionable the need to have standards of size at birth and growth to evaluate and contribute to guide the actions in the care of the newborn. For many years the references of Lejarraga and Fustiñana were used, progressively replaced by those of Fenton and Kim. However, recently, the INTERGROWTH-21st project has developed prescriptive growth standards to evaluate the size at birth from 33 weeks of gestational age, references from 24 to 32.