Critical Congenital heart diseases: Risk Factors

Critical Congenital heart diseases: Risk Factors 

Congenital heart diseases (CHD) are the most prevalent and serious of all recognised structural birth defects. Their estimated prevalence is 0.9%, which means that one in every 110 newborns is born with the disease. They are considered multifactorial in origin and as a result it is difficult to pinpoint a single cause for the defect. As the embryonic heart develops between 14 – 60 days of pregnancy, any issues arising during this phase in the form of infection or drugs in a genetically susceptible individual, can result in a serious CHD.   

The risk factors for critical congenital heart diseases can be classified into the following categories –  

1. INFECTIONS – Babies born to mothers with any febrile illnesses during the first trimester of pregnancy have a two-fold higher risk of developing CHD. Rubella infection, for instance, is an identified cause of CHD in this category.  
2. MATERNAL DRUG EXPOSURE – Therapeutic drugs strongly implicated for causing CHD include Lithium, Thalidomide anticonvulsants and isotretinoin. Usage of non-therapeutic drugs like cocaine by the mother in pregnancy also have a very strong association with serious CHD.  
3. MATERNAL MEDICAL CONDITIONS – About 1% of all CHD are attributed to this group. Common conditions like uncontrolled Diabetes Mellitus increase the risk of CHD to 5.3% as reported by the Atlanta Birth Defects case-control study. Additionally, maternal Phenylketonuria increases the risk of CHD by six-fold.  
4. MATERNAL HABITS – Alcohol consumption during pregnancy is a significant risk factor for CHD. Predominantly, ventricular septal defects and tetralogy of fallot are seen in babies of mothers who consumed alcohol during pregnancy. Similarly, maternal smoking in pregnancy is also considered a risk factor for CHD. 
5. PERICONCEPTUAL FOLIC ACID DEFICIENY – This too is a major risk factor for CHD. Studies have shown a 50% reduction in CHD after folic acid supplementation.  
6. ENVIRONMENTAL FACTORS – Ionizing radiation, exposure to pesticides and herbicides are known to increase the probability for serious CHD like transposition of great arteries and total anomalous pulmonary venous return. 
7. SOCIO-DEMOGRAPHIC FACTORS – Maternal age is also a considerable factor for CHD. Women younger than 20 years of age and older than 34 years of age, have increased risk of CHD. A serious heart defect called “Tricuspid Atresia,” is seen in babies born to mothers younger than 20.  Higher birth order also increases the risk of CHD.   Additionally, babies born to parents with a low socio-economic status also have a higher risk of CHD. 
8. GENETIC FACTORS – Chromosomal disorders like Down syndrome and Turner syndrome come with a high CHD risk, as do single gene disorders like NKX2-5 and TBX-5. 

90% of all serious CHD seen in infants are multifactorial, which means they develop due to a combination of different factors (genetic and environmental, maternal and socio- demographic); only 2% of these are environmental and 8% are genetic alone.  

To summarise, CHD has a major impact on human suffering and a high economic cost. Our main challenge is to prevent CHD through primary prevention, which would be possible thorough health awareness and genetic counselling.