What Are Congenital Heart Defects?

Understanding Congenital Heart Defects: Causes, Symptoms, Prevalence in India, and the Critical Role of Genetic Consultation

What Are Congenital Heart Defects?

CHDs occur when the heart or major blood vessels do not form correctly during the first 6–8 weeks of pregnancy. They range from simple, mild defects (such as small holes between heart chambers) that may close on their own to complex, life-threatening conditions requiring multiple surgeries.

Common types include:

• Ventricular septal defect (VSD) and atrial septal defect (ASD) — “holes in the heart”
• Patent ductus arteriosus (PDA)
• Tetralogy of Fallot
• Transposition of the great arteries
• Coarctation of the aorta
• Pulmonary or aortic valve stenosis
• Hypoplastic left heart syndrome and other complex lesions

Defects are broadly classified as cyanotic (causing bluish skin due to low oxygen) or acyanotic.

Causes of Congenital Heart Defects

In most cases, the exact cause remains unknown. CHDs usually result from a complex interplay of genetic and environmental factors.

Genetic factors play a significant role:

• Chromosomal abnormalities (e.g., Down syndrome/trisomy 21, Turner syndrome, trisomy 13 and 18)
• Microdeletion syndromes (most commonly 22q11.2 deletion/DiGeorge syndrome)
• Single-gene disorders (e.g., Noonan syndrome, Alagille syndrome, CHARGE syndrome)
• Familial inheritance patterns and de novo (new) genetic variants

Environmental and maternal risk factors include:

• Maternal diabetes (especially poorly controlled type 1 or type 2)
• Certain medications during pregnancy (e.g., isotretinoin, lithium, some anti-seizure drugs)
• Rubella or other viral infections in early pregnancy
• Alcohol use, smoking, or exposure to secondhand smoke
• Phenylketonuria (PKU) that is poorly controlled

Many cases are multifactorial, involving both genetic predisposition and environmental triggers.

Symptoms of Congenital Heart Defects

Symptoms vary widely depending on the type and severity of the defect. Some mild defects cause no symptoms and are discovered later in childhood or adulthood. Others present soon after birth.

In newborns and infants:

• Bluish tint to skin, lips, or nails (cyanosis)
• Rapid or difficult breathing
• Poor feeding, excessive sweating during feeds, or failure to gain weight
• Extreme sleepiness or lethargy
• Weak pulse or heart murmur

In older children and adults:

• Shortness of breath or easy fatigue with activity
• Irregular heartbeats (arrhythmias)
• Swelling in legs, feet, or abdomen
• Chest pain or fainting with exertion
• Recurrent respiratory infections

Many serious defects are now detected prenatally via fetal echocardiography or shortly after birth through newborn screening and clinical examination.

Prevalence of Congenital Heart Defects in India

CHDs affect approximately 8–9 out of every 1,000 live births. With India’s high birth rate, this translates to an estimated 200,000 to 240,000 babies born with CHD every year.
Of these, roughly one-fifth have serious defects requiring intervention in the first year of life. Ventricular septal defect is the most commonly diagnosed lesion in Indian children, followed by atrial septal defect. CHD accounts for a substantial proportion of infant deaths due to birth defects in the country.
Challenges in India include delayed diagnosis (especially in rural and semi-urban areas), limited access to specialized pediatric cardiac care outside major cities, and the impact of malnutrition on outcomes. Awareness and early referral remain critical.

Why Genetic Doctor Consultation Is Essential

Genetic evaluation and counselling are integral parts of comprehensive CHD care for several important reasons:

1. Identifying an underlying genetic cause — A genetic diagnosis is found in a significant proportion of cases (higher in syndromic or complex CHD). This can reveal associated non-cardiac issues (e.g., immune problems in 22q11.2 deletion, developmental concerns) that require monitoring or early intervention.
2. Recurrence risk assessment — Families often ask, “Will this happen again?” Genetic counselling provides personalized recurrence risk estimates for future pregnancies, which vary widely depending on the underlying cause.
3. Family screening and cascade testing — When a genetic cause is identified, at-risk relatives can be offered testing and screening.
4. Reproductive planning — For adults with CHD or parents of an affected child, genetic counselling helps with informed decisions about future pregnancies, including options for prenatal diagnosis or preimplantation genetic testing where appropriate.
5. Prognostic information — Certain genetic findings influence long-term cardiac and extracardiac outlook and guide multidisciplinary care.

Guidelines from organizations such as the American Heart Association emphasize that genetic counselling should be offered to individuals with CHD and their families, particularly in cases of complex, syndromic, or familial disease, and for adults with CHD considering parenthood.
As a clinical geneticist with dual training in obstetrics & gynaecology and medical genetics, I work closely with pediatric cardiologists, fetal medicine specialists, and families to provide accurate diagnosis, clear communication, and compassionate support throughout this journey.

Early Action Makes a Difference

If your child has been diagnosed with a congenital heart defect, if there is a family history of CHD or other birth defects, or if you are planning a pregnancy after having an affected child, a consultation with a genetic specialist can provide clarity and guidance.

Dr. Veronica Arora

Clinical Geneticist & Obstetrician-Gynaecologist Institute of Medical Genetics & Genomics

Sir Ganga Ram Hospital, New Delhi