Current growth standards, definitions, diagnosis and classification of fetal growth retardation.

Intrauterine growth retardation (IUGR) implies that intrauterine growth has been inhibited and that the fetus has not attained its growth potential. IUGR is a clinical term, and the diagnosis is usually based on small size for gestational age at birth (SGA). However, IUGR is not equal to SGA. Women seem to be programmed for having births of a certain size; some SGA babies are not IUGR, and some larger babies are still IUGR. A large number of growth charts, based on populations with different inclusion criteria and constructed according to different methods, have been developed and used; this complicates or invalidates comparisons between studies and populations. Growth charts (in percentiles) ought to be standardized and population-specific. In addition, the charts, when used as diagnostic tools, should allow for controlling for factors like sex and parity and, if possible, previous reproduction experience.