Causes are generally grouped into three categories: placental, maternal, and fetal. Placental causes, such as poor placental implantation or insufficiency, account for the majority of cases. Maternal causes include chronic hypertension, pre-eclampsia, diabetes with vascular disease, autoimmune conditions, smoking, and undernutrition. Fetal causes include chromosomal abnormalities, structural anomalies, congenital infections, and genetic syndromes. Genetic testing becomes particularly relevant when growth restriction is early-onset (before 32 weeks), severe, symmetric (affecting both head and body proportionately), or accompanied by structural anomalies on ultrasound. In such cases, chromosomal microarray analysis is generally recommended over standard karyotyping alone, as it detects smaller chromosomal deletions and duplications that karyotyping misses. Specific gene panels may also be considered when a genetic syndrome, such as Russell-Silver syndrome or Cornelia de Lange syndrome, is suspected clinically.