Fetal growth compromise: definitions, standards, and classification.

Fetal growth compromise is mostly defined by gestational age specific threshold value of birth weight or ultrasonically estimated fetal weight. The most frequently used threshold is the 10th centile. However, this approach can not differentiate fetal constitutional smallness from fetal growth failure. The most common descriptor terms are fetal growth restriction (FGR), intrauterine growth restriction and small for gestational age. It is recommended to restrict the use of the first two terms to prenatal assessment of growth and the last term to assessment of the birth weight. Growth reference charts are affected by physiological and methodological variables. There is controversy on whether the reference charts should be customized by multiple variables or inclusive of the whole population. Symmetric FGR is more common and has better outcome than asymmetric FGR. However, such a classification may not be clinically relevant.