The question every parent asks
"Is this my fault?" — I hear this question at every first consultation. A mother remembers the painkiller she took in the third week of pregnancy. A father thinks about his stress at work. A grandmother says "we never had anything like this in the family." Everyone is looking for a cause — and first of all, they are looking for it in themselves.
I want to answer this question honestly and in detail — because the wrong answer causes real harm. Parents who blame themselves manage their child's treatment less effectively, make decisions with greater difficulty, and carry an extra burden of guilt that helps neither them nor the child.
So — what does science say about the causes of congenital heart defects, and what is the parents' actual role?
What a congenital heart defect is and when it develops
A baby's heart forms in the first eight weeks of pregnancy. In this period it transforms from a simple tube into a complex four-chambered organ with valves, septa and major vessels. This is one of the most intricate processes in human embryonic development.
A congenital heart defect is a disruption of this formation — something went wrong in the genetic programme of development or in the external conditions in which it was occurring. The defect already exists by the time most women even discover they are pregnant.
Congenital heart defects are the most common type of congenital anomaly. They occur in roughly 1 in every 100 newborns. This is not a rarity — it is a medical reality that cardiac surgeons work with every single day.
Why it happens: what science says
The honest answer is this: in most cases, it is impossible to establish the precise cause. This is not evasion — it is a fact recognised by cardiology worldwide. Congenital heart defects arise in most cases through a complex interaction of genetic factors and environmental conditions, and separating those factors is extraordinarily difficult.
Nevertheless, science has identified a number of factors reliably associated with increased risk. It is important to understand: "increased risk" does not mean "cause." The majority of children born to mothers with these factors have healthy hearts. Conversely, the majority of children with heart defects have none of these factors.
Genetics: heredity and chromosomal abnormalities
A genetic component is present in approximately 20–30% of congenital heart defects. This means the child either has a change in a single gene or an abnormality in the structure of an entire chromosome.
The most well-known example is Down syndrome (trisomy 21). Children with this syndrome have heart defects in approximately 40–50% of cases. A similar association exists with Turner syndrome, Noonan syndrome, DiGeorge syndrome and a number of other genetic conditions.
Critically: chromosomal abnormalities in the vast majority of cases arise de novo — meaning they are not inherited from parents, but appear anew during cell division. Parents with a normal karyotype can have a child with a chromosomal anomaly — this is not their mistake, not their lifestyle, it is a chance event at the level of cell division.
A family history of heart defects does genuinely increase risk — if one parent has a heart defect, the probability for a child is approximately 3–5% (compared to the average population risk of about 1%). This is above average, but it still means that 95–97% of the time the child is born healthy.
Environmental factors: what actually matters
Approximately 2% of congenital heart defects are associated with established external factors. This is a small percentage, but it is important to know what it refers to.
Certain infections during pregnancy. Rubella contracted in the first trimester is the classic example — which is precisely why vaccination against rubella before pregnancy is so important. Cytomegalovirus, toxoplasmosis and several other infections are also associated with elevated risk of developmental abnormalities.
Certain medications. Retinoids (derivatives of vitamin A) used for acne treatment. Some anticonvulsant drugs. Lithium in high doses. Thalidomide — no longer in use but historically significant. The list is short and well known to obstetricians. Most common medications — penicillin-based antibiotics, paracetamol, antihistamines — are not on it.
Poorly controlled diabetes in the mother. Specifically poorly controlled — when blood sugar in the first trimester significantly exceeds the normal range. Well-compensated diabetes when planning pregnancy substantially reduces this risk.
Phenylketonuria in the mother without following the necessary diet during pregnancy.
Alcohol in large quantities. Fetal alcohol syndrome includes heart defects as one component. This refers to systematic heavy drinking — not a glass of wine before a woman knew she was pregnant.
What has not been proven to cause heart defects
This is perhaps the most important section — because this is where most parental guilt is concentrated, on things science does not connect to heart defects at all.
Stress during pregnancy. There is no convincing evidence that ordinary psychological stress — workplace conflict, anxiety, difficult life circumstances — causes heart defects. This is one of the most widespread myths, and it is not supported by research.
The mother's diet. Folate deficiency is linked to neural tube defects, but is not a proven cause of heart defects. The overall quality of diet, food cravings, nausea and inability to eat normally in the first trimester — none of this causes a heart defect.
Physical activity. Moderate exercise during pregnancy does not cause heart defects. This is a medical fact.
Computer use, mobile phones, microwave ovens. The electromagnetic radiation from household appliances is not a proven risk factor for congenital heart defects.
A single tablet taken before a missed period. One painkiller taken before a woman knew she was pregnant is not the cause of a heart defect. This question comes up very often — the answer is always the same.
The evil eye, a curse, or punishment. I say this directly, because I encounter it regularly in practice. A congenital heart defect is not the consequence of something parents did or did not do in a moral or spiritual sense.
Most cases remain unexplained
Here is the number worth remembering: in approximately 70–80% of congenital heart defects, the cause remains unknown. Not because medicine is failing. But because the heart forms through thousands of sequential biological processes, and a disruption in any one of them — often random and unpredictable — can lead to a developmental abnormality.
This is called multifactorial origin. There is no single button that was pressed to produce a defect. There is a complex interaction of dozens of factors, most of which lie entirely outside any person's control.
When parents ask me "why" — I answer honestly: in most cases, we don't know. This is not a failure — it is the current state of science. What matters more is this: we know how to treat it.
Are parents to blame — a direct answer
No. In the overwhelming majority of cases — no.
Parents do not choose their child's genetics. They do not control random mutations during cell division. They cannot prevent most of the factors that science identifies as associated with risk.
The only things parents can genuinely control are a few specific actions: getting vaccinated against rubella before pregnancy, managing diabetes, not taking teratogenic medications in the first trimester, avoiding alcohol. That is all. If you did these things — you did everything in your power. If you did not — your child's defect is still most likely unrelated, because in most cases the cause is unknown and unconnected to these factors.
Guilt does not heal a child. It takes away the energy needed to make decisions, to be present, to ask the right questions, and to support the child through treatment.
What to do with this knowledge
First: allow yourself to let go of guilt — as much as you can. This is a process, not a moment. But it can begin by stopping the search for your mistake where there is none.
Second: if you are planning another pregnancy, speak with a geneticist. After the birth of a child with a heart defect, a medical genetics consultation can help assess the real risks for future children. In most cases those risks are modest. But knowing is useful.
Third: focus on the present. The cause of the defect is the past. The treatment, the surgery, the recovery, your child's future — that is the present. And this is where your involvement makes a real difference.
I have seen children with the most severe defects live full lives — because their parents came forward in time, did not lose time searching for someone to blame, and were present at every stage of treatment. That is what is within your power.