Intrauterine growth restriction (IUGR) is an important clinical problem associated with increased perinatal mortality and morbidity. The most preferred small for gestational age (SGA) definition is birth weight below the 10th percentile, adjusted for gestational age. The incidence of IUGR is about 4 to 7 %. A variety of hormones are involved. IUGR may be due to chromosomal defects, smoking, early-onset preeclampsia ( < 34 weeks), connective tissue and inflammatory rheumatic diseases, maternal infections, several drugs, twin-to twin transfusion, anorexia nervosa, low maternal pre-pregnancy or small weight gain during pregnancy. High hemoglobin (Hb) levels during the first 10-20 weeks of pregnancy may also cause IUGR. Complications due to IUGR include fetal or neonatal death, dysmaturity, and physical as well as temporary or permanent mental defects. Low birth weight children may have behavioral problems, psychiatric disorders and lower intelligence test scores later in life. There is a relationship between IUGR, timing and progression of puberty, and polycystic ovary syndrome. Fetal changes of lipid metabolism and homeostasis in IUGR may place the grown adult at risk for hypertension, diabetes mellitus and coronary artery disease. Mothers of low weight offspring have an increased risk for cardiovascular and kidney disease later in life.