Congenital Malformations

Congenital Malformations - Shaping Gone Wrong

• Definitions:
  • Malformation: Primary structural defect; abnormal development (e.g., cleft lip).
  • Deformation: Altered shape by mechanical forces (e.g., clubfoot from oligohydramnios).
  • Disruption: Secondary breakdown of/interference with an originally normal developmental process (e.g., amniotic band syndrome).
  • Dysplasia: Abnormal cell organization into tissues (e.g., achondroplasia).

Peak teratogen sensitivity: Weeks 3-8 (organogenesis).

Major Teratogens & Effects:

• Chromosomal abnormalities (e.g., Down syndrome - Trisomy 21).
• Single gene mutations (e.g., Marfan syndrome).

⭐ The period of organogenesis, from week 3 to week 8 post-conception, is when the embryo is most susceptible to teratogenic agents causing major congenital malformations.

Neural Tube Defects - Brain & Spine Glitches

• Neural tube closure failure (3rd-4th week gestation).
• Diagnosis: ↑ Maternal Serum Alpha-Fetoprotein (MSAFP), ↑ Amniotic Fluid AFP & Acetylcholinesterase (AChE) (except spina bifida occulta). Ultrasound confirmation.
• Prevention: Folic acid supplementation (400 µg/day for general population; 4 mg/day for high-risk, e.g., prior NTD).

Major Types:

• Anencephaly:

  • Absence of forebrain, overlying skull, and scalp.
  • Fatal; often associated with polyhydramnios.

• Encephalocele:

  • Herniation of brain and/or meninges through a skull defect (cranium bifidum).
  • Commonly occipital.

• Spina Bifida: Defect in vertebral arch fusion.

  Type	Sac Contents	Key Features & Associations	AFP
  Spina Bifida Occulta	None (skin often overlies defect)	Often asymptomatic; may have skin tuft, dimple, lipoma.	Normal
  Meningocele	Meninges, Cerebrospinal Fluid (CSF)	Spinal cord usually in normal position; deficits rare.	↑
  Myelomeningocele	Meninges, CSF, neural tissue (cord/roots)	Neurological deficits below lesion; Arnold-Chiari II malformation common.	↑

⭐ Maternal intake of folic acid before conception and during early pregnancy significantly reduces the incidence of neural tube defects.

Cardiac Malformations - Heartbeat Blips

⭐ Ventricular Septal Defect (VSD) is the most common congenital heart defect overall, while Tetralogy of Fallot is the most common cyanotic congenital heart defect after the neonatal period.

-   Ventricular Septal Defect (VSD): Most common. Holosystolic murmur.
    ![Ventricular Septal Defect (VSD) Diagram](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Anatomy_Anatomical_Variations_and_Anomalies_Congenital_Malformations/984a87ea-2a2b-48df-85c4-3178cf0e3a8b.png)
-   Atrial Septal Defect (ASD): Fixed wide split S2.
-   Patent Ductus Arteriosus (PDA): Continuous machinery murmur. Close with **Indomethacin**; keep open with **Prostaglandin E1** for duct-dependent lesions.
-   Coarctation of Aorta: Blood pressure difference (Upper Extremity > Lower Extremity). Rib notching on X-ray. Associated with Turner's syndrome.

• Cyanotic Defects (R→L Shunt):
  • Tetralogy of Fallot (ToF): 📌 PROVe (Pulmonary stenosis, Right Ventricular Hypertrophy, Overriding aorta, VSD). Boot-shaped heart on X-ray. "Tet spells".
  • Transposition of Great Arteries (TGA): Severe cyanosis from birth. "Egg on a string" appearance on X-ray. Prostaglandin E1 vital for survival pre-surgery.
  • Truncus Arteriosus: Single arterial trunk supplies systemic, pulmonary, and coronary circulation.
  • Tricuspid Atresia: Absence of tricuspid valve, hypoplastic right ventricle. Requires ASD and VSD/PDA for viability.

GI & GU Malformations - Gut & Kidney Quirks

• GI Malformations
  • Tracheoesophageal fistula (TEF): Polyhydramnios. 📌 VACTERL (Vertebral, Anal, Cardiac, TEF, Renal, Limb).
  • Pyloric Stenosis: Non-bilious projectile vomiting (2-8 wks), 'olive' mass.

  ⭐ Pyloric stenosis typically presents with non-bilious projectile vomiting in infants aged 2-8 weeks and a palpable 'olive-shaped' mass in the epigastrium.

  • Hirschsprung Disease: Aganglionic megacolon; delayed meconium passage.
  • Duodenal Atresia: 'Double bubble' sign on X-ray; associated with Down syndrome.
  • Omphalocele vs. Gastroschisis:

    Feature	Omphalocele (Sac+)	Gastroschisis (Sac-)
    Location	Midline, umbilical ring	Right of umbilicus (usu.)
    Bowel	Normal	Edematous, matted
    Anomalies	Common (cardiac, chrom.)	Less common (atresia)

• GU Malformations
  • Hypospadias: Ventral urethral opening.
  • Epispadias: Dorsal urethral opening; often with bladder exstrophy.
  • Horseshoe Kidney: Fused lower poles; trapped by Inferior Mesenteric Artery.
  • Posterior Urethral Valves (PUV): Male urethral obstruction; hydronephrosis.
  • Renal Agenesis: Potter sequence (oligohydramnios → pulmonary hypoplasia, facial/limb defects).

High‑Yield Points - ⚡ Biggest Takeaways

• TORCH infections are major teratogenic agents causing diverse congenital malformations.
• Neural Tube Defects (NTDs) are largely preventable with maternal folic acid supplementation.
• Organogenesis (embryonic weeks 3-8) is the critical period for teratogen-induced malformations.
• VACTERL association is a recognized pattern of multiple congenital anomalies.
• Potter sequence, due to oligohydramnios, features pulmonary hypoplasia and characteristic facies.
• Amniotic band syndrome can cause constrictive defects, amputations, and fetal disruptions.