Medical Emergencies · patient case question
Which maternal factor is a recognised risk factor for tetralogy of Fallot?
Patient case: Child with tetralogy of Fallot presenting for a dental examination
Patient: Male, 5 years old
Chief Complaint: Mother: “He needs a check-up and I was told two of his back teeth have cavities.”
Background: Tetralogy of Fallot diagnosed in infancy, NOT yet repaired. Mother reports the pregnancy was unplanned and she took no prenatal vitamins. Episodes of cyanosis on exertion. Followed by a paediatric cardiologist, last seen fourteen months ago.
Vital Signs: BP 92/58 mmHg · HR 108 bpm · SpO₂ 91% on room air · T 98.6°F
Findings: Mild central cyanosis and clubbing of the fingers. Occlusal caries in #B and #I. Generalized plaque. No acute infection.
Show answer and explanation
Correct answer: D. Inadequate folic acid supplementation during pregnancy
- A. Vitamin C deficiency in pregnancy is rare in developed settings and is associated with connective tissue and bleeding problems, not cardiac septation defects.
- B. Maternal iron deficiency causes anaemia, low birth weight and preterm delivery. It is not linked to conotruncal cardiac malformation.
- C. Excess calcium intake is not teratogenic and has no association with congenital heart disease.
- D. CORRECT. FOLIC ACID deficiency in early pregnancy is an established risk factor for congenital heart defects, tetralogy of Fallot among them, alongside neural tube defects and orofacial clefts. The defect arises from anterocephalad deviation of the outlet septum during the fourth to eighth week of gestation — before many women know they are pregnant, which is precisely why periconceptional supplementation is recommended. Other recognised risks are maternal diabetes, phenylketonuria, rubella, alcohol, retinoic acid, and the chromosomal associations with 22q11.2 deletion (DiGeorge) and trisomy 21.
Note: The four components of tetralogy of Fallot, from the single embryologic error: PULMONARY STENOSIS (right ventricular outflow obstruction), VENTRICULAR SEPTAL DEFECT, an OVERRIDING AORTA, and RIGHT VENTRICULAR HYPERTROPHY. Mnemonic: PROVe. Right-to-left shunting through the VSD is what produces the cyanosis.
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