environmental agents (teratogens) an agent which can cause...
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Environmental agents (teratogens)
An agent which can cause a birth defect by interfering with normal embryonic or fetal development is known
as a teratogen
The potencial effect of any particular teratogen depends on:
dosage and timing when it is administered during the pregnancy
susceptibility of both mother and her unborn baby
Maternal infections
Several infectious agens can interfere with embrygenesis and fetal development. The developing brain, eyes and ears are particularly susceptible to damage by infection
Viruses
CytomegalovirusHerpes simplexRubellaVaricella zoster HIV
Teratogenic effects of the rubella virus
microcephaly
microphtalmia
cardiac defect
psychomotoric retardation
Rubella syndrome
The symptoms of the infections during embryonicand fetal developmentMicrocephalyMental deficiency DeafnessMicrophtalmia ChorioretinitisGrowth deficiency
Early infancytrombocytopenia, anemiahepatosplenomegalyobstructive jaundiceinterstitial pneumonia
Drugs with proven teratogenic effects in human
ACE inhibitors renal dysplasiaAlcohol microcephaly, cardiac defect
typical faciesChloroquine chorioretinitis, deafnessDiethylstillboestrol uterine malformation
vaginal adenocarcinomaLithium cardiac defectRetinoids ear and eye defectPhenytoin cardiac defect, cleft palate
digital hypoplasiaStreptomycin deafness Tetracyclin dental, enamel hypoplasiaThalidomid phocomeliaValproic acid neural tube defectWarfarin nasal hypoplasia, stippled
epiphysis
Teratogenic effects of the folic acid antagonist
mental retardaton
growth deficiency
craniofacial abnormalitieshypoplasia of frontal bonebroad nasal bridgeprominent eyes micrognathia, cleft palate
Aminopterin syndrome
Fetal hydantoin syndrome
mild to moderate growth deficiencymild mental deficiencycraniofacial abnormalities
ocular hypertelorismbroad nasal bridgelow set abnormal earscleft lip and palatehypoplasia of distal phalanges micro - brachycephaly
Fetal hydantoin syndrome
Fetal trimethadione syndrome
prenatal onset growth deficiency brachycephalymild midface hypoplasiacleft lip and palate cardiovascular abnormalities genitourinary abnormalities
Fetal valproate syndrome
Fetal warfarin syndrome
developmental and mental deficiency
hypotonia, seizures, optic atrophy
hypoplastic nose with low nasal bridge
stippled mineralization in epiphyses, vertebrae,nasal cartilage
Fetal warfarin syndrome
Chemicals which have a proven teratogenic effect in humans
Clinical features Organic mercurials microcephaly
developmental delay seizures
Polyhalogenated biphenyls growth retardation exophtalmus“cola collor baby“
Dioxin, xylen caudal regression syndrome
Pesticides, heavy metals mental retardation ? Littleinformation available
The fetal alcohol syndrome Prenatal use of ethanol can result in wide
spectrum of foetal alcohol effects
Clinical findings
growth retardationmental retardation
microcephalylong smooth philtrumshort palpebral fissures
midfacial hypoplasia
Fetalalcohol
syndrome
Physical agens as a teratogen
Ionizing radiation
Heavy doses of ionizing radiation, far in excessof those used in routine diagnostic radiography, can causemicrocephaly and ocular defectsThe most sensitive time of exposure is from 2-5 weeksafter conception. Ioniz. radiation can also have mutagenicand carcinogenic effects. Risks associated with low dosediagnostic procedures are minimal.
Prolonged hyperthermia
Fetal hyperpyretic syndrome
Defects of CNS : defect of neuronal migratonmicrocephally neural tube defectsdevelopmental delayseizures
MicrophtalmiaFacial defects micrognathia
cleft lip and palatae
Fetal hyperpyretic syndrome
Maternal metabolic, genetic and nutritional factors
Maternal phenylketonuria – serious demage to the fetuspsychomotoric delay
Iodine deficiency mental retardation
Diabetes mellitus insulin dependent – threefold increasein incidence of congenital malformation –
cardiac defectscaudal regression syndrome
Maternal epilepsy cleft lip and palateneural tube defects