Fetal growth restriction (FGR) is etiologically associated with various maternal, fetal and placental factors, although such an association may not be present in many cases. Maternal factors include hypertensive diseases, autoimmune disorders, certain medications, severe malnutrition, and maternal lifestyle including smoking, alcohol and cocaine use. Fetal etiologies include aneuploidy, malformations, syndromes related to abnormal genomic imprinting, perinatal viral or protozoan infections, preterm birth, and multiple gestation. Placental factors may involve many conditions including anatomical, vascular, chromosomal and morphological abnormalities. Better understanding of these etiologic conditions may lead to improved prediction, prevention and management of FGR.