9. Some of the important factors are as follows:

chromosomal abnormality, genetic disorders, infections in mother during the first three months of pregnancy. Some common infections that affect the developing brain of the foetus are rubella, herpes, syphilis, CMV, toxoplasmosis, maternal diseases like diabetes mellitus, high blood pressure, hypothyroidism and hyperthyroidism, malnutrition, exposure to X-rays in the early months of pregnancy, using harmful drugs, maternal-fetal blood incompatibility: Rh factor, maternal use of alcohol, drugs and smoking.