Teratology Flashcards
Teratology
Teratology is the science of:
- Congenital developmental disorders
-Overt or latent defects of the organism resulting from effect of internal and external factors on developmental processes.” (Ujházy et al, 2012)
Teratology- Etymology
Terat = sign sent by the gods, portent, marvel, monster
Ology = doctrine, theory, science of (Mirriam-Webster)
Signal to noise ratio
High signal-noise ratio means easier to detect he signal
Low signal- noise ratio means it is harder to detect the signal
Bradford Hill Criteria
- Temporality: cause must precede the outcome
- Strength: strong relationship between variables
- Biological gradient: dose-response effect: More exposure leads to more outcome
- Consistency: relationship is consistent in different studies and populations
- Specificity: single cause for single effect
- Plausibility: biological rationale for relationship
- Coherence: relationship consistent with previous knowledge
- Analogy: relationship synonymous with other, similar, relationships
-Experiment/intervention: randomly assigned treatment changes the outcome
Some known teratogens
Medications:
- SSRIS
- Statins
- Anticonvulsants
- Thalidomide
Drugs:
- Alcohol
- Tobacco
- Cocaine
- Amphetamines/meth/MDMA
Opiates (eg: heroin)
Conditions and infections:
- Hypotension
- Toxoplasmosis
- Rubella
- Diabetes
Environmental exposures:
- Heavy metals
- Radiation
- Pesticides
- Fluoride
Thalidomide – the first famous teratogen
- Anti-nausea drug developed in 1950s, and sold in UK as treatment for symptoms, including morning sickness in pregnancy
- Sold under brand name Distaval among others
- Took 5 years for authorities to realise the drug was causing birth defects
- Prenatal exposure to thalidomide can cause damage to limbs, internal organs and the brain
Prenatal exposure to medications
- Studies on the neurodevelopmental impact of prenatal exposure to antidepressants tend to find null results, but some evidence of impaired motor function (Review: Gentile &Galbally, 2011)
- Broader literature review onimpact of psychotropic medications (antidepressants, benzodiazepines, mood stabilizers) found antidepressants linked to reduced IQ and impaired language performance
- Same review warned that research on the neurodevelopmental impact of psychotropic medications is limited and focuses on physical birth defects (Gentile, 2021)
- Some studies show an effect of prenatal paracetamol exposure and asthma (Barańska etal, 2023), and neurodevelopmental outcomes including ADHD, ASD, or lower IQ (Baueret al, 2018)
-The NHS advice is that paracetamol is safe to use in pregnancy but should be used sparingly
Sodium Valproate
- An anticonvulsant medication used mostly for epilepsy, seizures, bipolar and migraines
- Contraindicated in pregnancy and carried a warning label
- In some with epilepsy is the only effective medication so doctor might recommend they continue to use it in pregnancy
- Exposure to valproate in pregnancy associated with a range of physical birth defects and developmental problems (Foetal Valproate Spectrum Disorder(FVSD)
- Not all people with prenatal exposure to valproate will develop FVSP – dose-response relationship, where higher exposure carries a higher riskof FVSD
Foetal Valproate Spectrum Disorder- Developmental features
- Cognitive delay/low IQ
- Academic delay
- Sensory processing difficulties
- Motor control/ movement difficulties
- Language and communication difficulties
- Autism very common
Foetal Valproate Spectrum Disorder- Facial features
- Hypotelorism
- Flat midface
- Small upturned nose
- Shallow philtrum
- Low set ears
- Smal mouth
Impact of maternal prenatal stress on the foetus- mechanisms
- When we experience stress, stress hormones (adrenaline, cortisol, corticotropin-releasing hormone (CRH), adrenocorticotropin-releasing hormone (ACTH)) are released into our blood
-The placenta acts as a barrier, protecting foetus from many harmful compounds, but stress hormones (and all teratogens) pass through and into the blood of foetus
The impact of maternal prenatal stress on the foetus – physical conditions
- Spontaneous abortion
- Structural malformations
- Preeclampsia
-Preterm birth
-Low birth weight
The impact of maternal prenatal stress on the foetus – animal models
Experiments using rats and monkeys showed prenatal stressors delivered to the pregnant mother (such as being tied up, or given an electric shock) lead to changes in offspring:
- Delayed motor development
- Reduced exploration and adaptive behaviour
- More emotional and anxious reactions to unfamiliar stimuli
- Impaired cognitive function
- Alterations in social and sexual behaviour
(Mulder et al, 2002; Beydoun & Saftlas, 2008
The impact of maternal prenatal stress on the foetus – human functional development
Such studies in humans have found prenatal stress is related to:
- Externalising behavioural problems
- Anxiety
- Low mood / emotional problems
- ADHD symptoms
- Motor difficulties
- Low IQ Speech and language difficulties
- Impulsivity
(Beydoun & Saftlas, 2008; Talge et al, 2007
Heavy metals (HMs)
- Elements having an atomic number greater than 20 and atomic density above 5 g cm− 3
- Can be ingested in food, breathed in though air or from metal-based pesticides,tobacco smoke, and other environmental exposures