Teratogens Flashcards
Prenatal period
Embryonic development week 3-8
Fetal development week9 - until birth
Postnatal 0-25 years old
During this an organ is vulnerable to internal abnormalities and external factors
Altering can cause birth defects and defects that become apparent in later life
Teratogen
Agent that causes birth defects in embryos.
In the US 1 in every 33 babies has problems
Wilsons principles of teratology 1
1) susceptbility to Teratogenesis depends on the genotype of the conceptus and the manner in which this interacts with adverse environmental factors.
Dilantin is an anti-epileptic medication. If taken in pregnancy 5-10% of babies become affected however this is determined by the genotype
Wilsons principle of teratology 2
Susceptability to teretogenesis varies with the developmental stage at the time of exposure to an adverse influence.
Zygotic period 0-2 weeks - Placental disconnection with maternal bloodstream
Embryonic period 3-8 weeks - Critical developmental stage for organ formation
Fetal period 9 weeks onwards - Potential for tissue damage and growth retardation
Wilsons principle of teratology 3
Teratogenic agents act in specific ways on developing cells and tissues to cause abnormal developmental events.
Abnormal amounts of inductive signals can become teratogens - RA - metabolite of vitamin A
Wilsons principle of teratology 4
The access of adverse influences to developing tissues depends on the nature of the influence.
High does of ionising radiation from x-rays.
Affects rapidly-dividing cells
Increased DNA mutations
Highest risk during zygotic/embryonic period
Wilsons principle of teratology 5
The four manifestations of deficient development are death, malformation, growth retardation, and functional deficit
Teratogens may cause one or more of these effects in the developing organisim
These effects are often interdependent
A specific effect may be more likely during a specific developmental period
Wilsons principle of teratology 6
Manifestations of deviant development increase in frequency and degree as dosage increases, from the no-effect to the totally lethal level.
Some teratogens may have no effect at low doses.
effect severity increases with dosage until plateau
Repeated exposure results in accumulation of effect size
Physical teratogens
X-rays or gamma rays
Embryonic death, increased DNA mutations and cancer risk, slow fetal growth and or malformations
Hyperthermia
Abnormally high temp of pregnant mother
-Neural tube defects
-Spontaneous abortions
-Cardiovascular abnormalities
Infections
Micro-organisms = rubella
High risk of developing congenital rubella syndrome in first trimester
-Cardiac defects, deafness
-eye anomalies
-Microcephaly
-the earleir the greater the malformations
-Spontaneous abortions, still-born
Rubella was eliminated in 2004 because of vaccines
Chemicals - prescription drugs
Retinoic acid
Thalomide - given to mothers to prevent morning sickness - critical period for limb formation leading to babies being born without long bones in their arms and legs
Aspirin - Low birth weight, infant death, poorer motor development, attention deficits, lower intelligence
Chemicals - non-prescription drugs alcohol
Alcohol - Fetal alcohol spectrum disorder - facial abnormalities, cleft pellet and sometimes lip
Later defects;
mental retardation, impaired motor coordination, ADHD, slow physical growth.
Severe exposure affects brain size
Ethanol affects specific neural crest cells in the developing craniofacial features .
Disrupts sonic hedgehog - Levels are decreased by alcohol exposure
Non-prescriptive drugs - Tobacco
Low birth weight
Prematurity
Impaired breathing during sleep
Increased pacenta previa
Miscarriage
Infant death
Cancer later in childhood
Cleft lip
Nicotine constricts blood vessels and causes placenta to grow abnormally
Nicotine raises carbon monoxide in the bloodstream - likely to slow fetal growth and may damage the CNS
Non-prescription drugs - cocaine, heroin, methadone
Prematurity
low birth weight
Physical defects
Breathing problems
Death around the time of birth
Babies often born drug-addicted
Precise effect difficult, multi-drug users
Environment chemicals
Pesticides, herbicides
Bisphenol A - industrial chemical in plastic products, bottles, plasticised cardboard, medical devices.
