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Foundation Sciences · Embryology
Teratogens and Critical Periods
Teratogens are environmental agents (drugs, infections, radiation) that disrupt embryonic or foetal development; effects depend on agent, dose and timing.
📌 Learning Objectives
- Describe the underlying mechanism of Teratogens and Critical Periods.
- Identify the key clinical features and complications of Teratogens and Critical Periods.
- Outline the appropriate investigations and management of Teratogens and Critical Periods.
- Discuss the implications for patients and families of Teratogens and Critical Periods.
📋 Overview
Greatest sensitivity is during organogenesis (weeks 3–8). Common teratogens include alcohol, thalidomide, retinoids, valproate, warfarin, lithium, ACE inhibitors and infections (TORCH).
🔬 Basic Science
Greatest sensitivity is during organogenesis (weeks 3–8). Common teratogens include alcohol, thalidomide, retinoids, valproate, warfarin, lithium, ACE inhibitors and infections (TORCH).
🏥 Clinical Relevance
Sodium valproate carries a high risk of major congenital malformations and neurodevelopmental disorders; avoid in pregnancy.
🧪 Investigations
Investigation depends on clinical context: relevant blood tests, imaging, and specific genetic or histopathological tests as appropriate. Refer to specialist services where indicated.
💊 Management
Management is condition-specific and typically multidisciplinary, combining medical therapy, surgical intervention where appropriate, supportive care, and family/genetic counselling.
Revision Resources – expand the sections below for high-yield notes, exam pearls, key facts and further reading.
MLA High-Yield Notes & Quick Revision ⌄
Common SBA themes: recognising the underlying mechanism, identifying classic clinical features, and choosing the first-line investigation or management step. Watch for inheritance pattern and characteristic associations.
teratogen
fas
valproate
warfarin
torch
- Organogenesis (weeks 3–8) is the period of greatest teratogenic susceptibility.
- Foetal alcohol syndrome features small palpebral fissures, smooth philtrum and thin upper lip.
- Sodium valproate causes neural tube defects, cardiac and craniofacial defects.
- Warfarin causes nasal hypoplasia and stippled epiphyses (foetal warfarin syndrome).
- ACE inhibitors are teratogenic in the second and third trimesters (oligohydramnios, renal damage).
Exam Pearls ⌄
⭐ High Yield
Organogenesis (weeks 3–8) is the period of greatest teratogenic susceptibility.
Foetal alcohol syndrome features small palpebral fissures, smooth philtrum and thin upper lip.
Sodium valproate causes neural tube defects, cardiac and craniofacial defects.
Warfarin causes nasal hypoplasia and stippled epiphyses (foetal warfarin syndrome).
ACE inhibitors are teratogenic in the second and third trimesters (oligohydramnios, renal damage).
💡 Clinical Pearl
Teratogen: Sodium valproate carries a high risk of major congenital malformations and neurodevelopmental disorders; avoid in pregnancy.
⚠️ Exam Tip — Common Mistakes
Confusing the mechanism of Teratogens and Critical Periods with related conditions.
Missing classic clinical features of Teratogens and Critical Periods in SBA stems.
Failing to consider Teratogens and Critical Periods in the differential diagnosis.
Key Facts ⌄
Organogenesis (weeks 3–8) is the period of greatest teratogenic susceptibility.
Foetal alcohol syndrome features small palpebral fissures, smooth philtrum and thin upper lip.
Sodium valproate causes neural tube defects, cardiac and craniofacial defects.
Warfarin causes nasal hypoplasia and stippled epiphyses (foetal warfarin syndrome).
ACE inhibitors are teratogenic in the second and third trimesters (oligohydramnios, renal damage).
Related Topics ⌄
References ⌄
- GMC MLA Content Map
- NICE Clinical Knowledge Summaries
- BMJ Best Practice
Further Resources
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