Teratogenesis.

Owner

U

Untitled

Verification

Tags

TERATOGENESIS – DRUGS (COMPLETE NOTE)

Key principles (EXAM FIRST)

Greatest risk = 3–8 weeks gestation (organogenesis)
Effect depends on:

Drug
Dose
Timing

Teratogens cause structural malformations, not just growth issues
Some drugs cause functional defects even later in pregnancy

MASTER TABLE – TERATOGENIC DRUGS

Drug / Group	Major Fetal Effects	Classic Exam Hook
Alcohol	• Growth restriction • Microcephaly • Intellectual disability • Facial anomalies (smooth philtrum, thin upper lip, short palpebral fissures) • Cardiac defects (VSD)	Most common preventable cause of intellectual disability
Isotretinoin (Vitamin A)	• Craniofacial anomalies (cleft lip/palate, microtia) • CNS defects (microcephaly, hydrocephalus) • Conotruncal heart defects • Thymic hypoplasia	Absolutely contraindicated (Category X)
Thalidomide	• Limb reduction defects (phocomelia) • Ear & eye defects • Cardiac, renal, GI anomalies	Phocomelia = thalidomide
Valproate	• Neural tube defects (spina bifida) • Facial dysmorphism • Developmental delay	Highest NTD risk among AEDs
Carbamazepine	• Neural tube defects (lower than valproate)	AED → think NTD
Phenytoin	• Fetal hydantoin syndrome • Craniofacial anomalies • Hypoplastic nails, growth restriction	Anticonvulsant facial pattern
ACE inhibitors / ARBs	• Renal agenesis/dysgenesis • Oligohydramnios • Pulmonary hypoplasia • Skull hypoplasia	2nd–3rd trimester renal failure
Warfarin	• Nasal hypoplasia • Stippled epiphyses (chondrodysplasia punctata) • CNS hemorrhage	Warfarin embryopathy
Lithium	• Ebstein anomaly	Lithium → Tricuspid valve
Methotrexate	• Craniofacial anomalies • Limb defects • Growth restriction	Folate antagonist
Tetracyclines	• Tooth discoloration • Enamel hypoplasia • Bone growth inhibition	Yellow-brown teeth
Aminoglycosides	• Ototoxicity (VIII nerve damage)	Sensorineural deafness
Sulfonamides	• Kernicterus (near term)	Displace bilirubin
NSAIDs (late pregnancy)	• Premature closure of ductus arteriosus	Avoid in 3rd trimester
Diethylstilbestrol (DES)	• Clear cell adenocarcinoma of vagina • T-shaped uterus	Young woman + vaginal cancer
Androgens	• Virilization of female fetus	Ambiguous genitalia
Misoprostol	• Limb defects • Cranial nerve palsies	Failed abortion attempts
Cocaine	• Placental abruption • Growth restriction	Vasoconstriction

ULTRA-HIGH-YIELD PAIRINGS (EXAM RAPID FIRE)

Defect	Drug
Craniofacial anomalies	Isotretinoin
Limb reduction (phocomelia)	Thalidomide
Neural tube defects	Valproate > Carbamazepine
Renal agenesis	ACE inhibitors / ARBs
Ebstein anomaly	Lithium
Tooth discoloration	Tetracyclines
Stippled epiphyses	Warfarin
Deafness	Aminoglycosides / Rubella
Intellectual disability	Alcohol

EXAM STRATEGY

If question mentions POA 4–8 weeks → think structural defects
If renal + oligohydramnios → ACE inhibitors
If limb absent → thalidomide
If NTD + epilepsy → valproate
If acne drug + pregnancy → isotretinoin

ONE-LINE EXAM LOCK

“Isotretinoin → face & heart; Thalidomide → limbs; Valproate → neural tube; ACE inhibitors → kidneys; Warfarin → cartilage.”