Agents and conditions that can harm the prenatal brain, impairing the future child's intellectual and emotional functioning, are called

behavioral teratogens.
Examples of teratogens are viruses, drugs, chemicals, stressors and even malnutrition. Although teratogens always pose a risk for developing embryos, some do not cause immediate damage. Other factors should also be considered. Factors like the developmental stage the pregnancy, dose, and frequency of exposure, and the genetic makeup of the embryo.