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Teratogenic Agents and Their Effect on Child HealthBy

Prof. Ali Shaltout

Definition of Teratogen

Any agent that can produce malformation (birth defect), by interfering with normal embryonic development

Teratogen acts on somatic cells of the developing organism




Somatic cells

Germ cells


Genetic material


Factors Affecting Teratogenicity1.

Time of exposure: Exposure to the teratogen is usually for short period Teratogenic event exposure must occur a considerable time before the developmental


Dosage: Maternal response The ability to metabolize the chemical

2. 3.

Heriditary predisposition Specificity of teratogens



Approximately 6.5% of all birth defects are attributed to teratogens


Knowledge of: Which agents are potential teratogens and their effect on the developing fetus

Is important: Because limiting exposure to teratogens is an effective way to prevent birth defects

Teratogenic Agents: 1. Durgs and chemicals 2. Maternal infections 3. Physical agents: Ionizing radiation Prolonged hyperthermia 4. Maternal diseases

Common Teratogenic DrugsDrugAlcohol Lithium Phenytoin Chloroquine Penicillamine Warfarin Streptomycin Tetracycline Valproic acid: Retinoids Thalidomide Fetal alcohol syndrome Ebstein anomaly Cardiac defects, cleft palate, hypoplastic nails Chorioretinitis, deafness Cutis laxa syndrome Nasal hypoplasia - Stippled epiphyses Deafness Enamel hypoplasias Neural tube defects Eye & ear defects, Hydrocephalus Phocomelia



Fetal Alcohol Syndrome

Growth retardation (prenatal & postnatal) Microcephaly Developmental delay Skeletal and cardiac anamalies Characteristic facies: (mid face hypoplasia) Short palpebral fissure Epicanthic folds Smooth philtrum Thin upper lip Short, upturned nose

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Maternal Infections

Several infectious agents can interfere with embryogenesis and fetal development

The developing brain, eyes and ears are particularly susceptible to damage by infection


Infectious Teratogenic AgentsInfection:Viruses Cytomegalovirus Herps simplex Varicella zoster Bacteria: Syphilis Parasites: Toxoplasmosis

EffectsChorioretinitis, deafness, microcephaly Microcephaly, cataracts, retinitis, cardiac defects Microcephaly, chorioretinits, skin defects Hydrocephalus, Osteitis, retinitis Hydrocephalus, microcephaly, cataracts, chorioretinitis, deafness

Congenital Rubella Syndrome Cardiac: pulmonary artery stenosis (55%)



Deafness Cataracts, Glaucoma, retinopathy Mental retardation IUGR Neonatal Purpura, Hepatosplenomegaly

Ionizing Radiation

Heavy doses of ionizing radiation Microcephaly and occular defects The most sensitive time of exposure is from 2 to 5 weeks after conception Risks of low-dose diagnostic procedures minimal are

Prolonged hyperthermia Prolonged hyperthermia in early pregnancy

Microcephaly Microphthalmia Encephalocele Excessive

use of hot baths and saunas

during the first trimester should be avoided

Maternal diabetes mellitus

Most common malformation in infants of diabetic mother include: Congenital HT D Neural tube defects Lumbo sacral dysgenesis, Holoprosencephaly Small left colon syndrome Renal disorders: double ureter, renal vein thrombosis, renal agenesis

Maternal phenylketonuria

High level of phenylalanine in pregnant woman with PKU not on special diet serious damage to the fetus: Mental retardation (100%) Microcephaly Congenital heart defects

Congenital rubella syndrome is characterized by all of the following except:1. 2. 3. 4. 5.

Growth retardation Deafness PDA Macrocephaly Cataracts


Are the following statements true or false?1.

There may be individual difference in sensitivity to specific teratogens T F Teratogen acts on germ cells and alter the genetic material T F Prolonged hyperthermia in the first trimester may have potential teratogenic effect T F Maternal IDDM associated with two to three fold increase in incidence of congenital malformations in offspring T F




Match each of the following teratogenic agents with their most common effect on offspring

1. 2. 3. 4. 5.

Valproic acid Maternal phenylketonuria Thalidomide Maternal DM Lithium

( ) Ebstein anomaly ( ) Phocomelia ( ) Neural tube defects ( ) Small left colon syndrome ( ) Mental retardation



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