If you are reading this right after a diagnosis: You are probably searching for what you did wrong. You did not do anything wrong. That is not just reassurance — it is the scientific answer. This page explains why.
The question almost every parent asks
When a child is diagnosed with Poland anomaly, the first question parents ask — especially mothers — is almost always the same: Did I cause this?
They search their memories. Was it the medication they took before they knew they were pregnant? The glass of wine at a holiday party in the first week? The stress at work? The fall? The infection? Something they ate?
The guilt can be crushing, and it is almost always silent. Parents rarely say it out loud, even to each other.
We want to answer that question directly, and we want to answer it with the science behind it — not just a reassuring platitude. Because when you understand how Poland anomaly actually happens, the guilt doesn't just ease. It becomes medically, biologically impossible to sustain.
What actually causes Poland anomaly
Poland anomaly results from a brief interruption to blood supply in a very specific area of the developing embryo, at a very specific moment in early pregnancy.
During approximately the sixth week of gestation, the subclavian artery and its branches — particularly the axillary artery — supply blood to the tissue that will become the chest wall, the pectoral muscle, and in some cases the hand and forearm on one side of the body. If blood flow through this artery is temporarily disrupted at that moment, the affected tissue does not develop normally.
The result is Poland anomaly: partial or complete absence of the pectoralis major muscle, sometimes with involvement of the ribs, the breast, and the hand on the same side.
This explanation — called the vascular disruption hypothesis — was first proposed by Dr. Bamforth and colleagues and has become the most widely accepted scientific explanation for Poland anomaly. It is cited in the AISP 2020 international consensus guidelines, the most comprehensive clinical reference on Poland anomaly published to date.
Why nothing you did caused it
Week 6 of gestation is the key detail. Most women do not know they are pregnant at week 6. The average pregnancy is confirmed around week 4 to 6 — meaning this disruption occurs right at the moment of, or before, most women even take a pregnancy test.
More importantly: the vascular disruption that causes Poland anomaly is not triggered by anything external. It is not caused by:
- Medications (including common over-the-counter drugs taken before a confirmed pregnancy)
- Alcohol consumed before a confirmed pregnancy
- Physical activity, exercise, or exertion
- Stress, anxiety, or emotional trauma
- Diet, nutrition, or anything eaten or not eaten
- Falls, accidents, or physical impact
- Infections or illnesses
- Environmental exposures
- Anything a father did before or during conception
The disruption is random. It happens in the same way that a blood vessel can momentarily spasm or compress — a tiny, brief, biological event with no external cause and no warning. It is not predictable, not preventable, and not the result of any choice made by either parent.
Is Poland anomaly genetic? Could it happen again?
In the vast majority of cases, Poland anomaly is not genetic. It is called a sporadic condition — meaning it occurs by chance, not because of an inherited gene. It does not typically run in families, and having one child with Poland anomaly does not meaningfully increase the likelihood of it occurring in another pregnancy.
There are rare case reports of Poland anomaly appearing in multiple family members, which researchers continue to study. But these cases are exceptional. The medical consensus is that Poland anomaly is sporadic in nature.
This also means there was no gene you passed on, no carrier status to worry about, and no hereditary risk to communicate to siblings or other family members in most cases. If you have specific concerns about recurrence risk, a pediatric geneticist can review your family history and provide guidance tailored to your situation.
What the research says
The AISP — the Italian Association for Poland Syndrome, which published the first international consensus guidelines on Poland anomaly in 2020 — describes the cause as a disruption to the subclavian artery and its branches during early embryonic development. Multiple published case series and review articles across several decades support this explanation.
No published research has identified any maternal behavior, exposure, or lifestyle factor as a cause of Poland anomaly. Researchers have specifically looked for patterns — trying to identify whether any shared exposure might explain clusters of cases — and have not found one. The condition does not cluster around geographic locations, occupational exposures, medication use, or any other identifiable environmental factor.
The science is not ambiguous on this point. Poland anomaly is a random developmental event.
You did not cause this. Not by something you took. Not by something you ate. Not by something you felt. Not by something you did or did not do. The vascular disruption that causes Poland anomaly happens before most women know they are pregnant, it has no known external trigger, and it is not preventable. The medical and scientific community is unified on this.
The only thing you could have done to prevent it would have been to know, six weeks into an unconfirmed pregnancy, that a specific blood vessel in your embryo was going to experience a brief, random, microscopic event — and that is not something any parent, any doctor, or any technology in existence can detect or prevent.
You were not at fault. You are not at fault. You could not have stopped this.
If you are still struggling with this
Knowing the science does not always make the guilt go away immediately. That is completely normal. The feeling that we should have been able to protect our child is deeply human, and it does not respond to logic alone.
Many parents find it helpful to connect with others who have been in exactly the same place — parents who asked the same questions and found their way through them. The Poland Foundation community forum is one place to do that. Organizations like the Lucky Fin Project also have large, active communities of parents who have navigated these feelings and are willing to talk.
If the guilt is significantly affecting your daily life, speaking with a therapist or counselor who works with parents of children with medical conditions can also be genuinely helpful. This is not a small thing to carry, and you do not have to carry it alone.
Questions to bring to your child's care team
At your next appointment with your child's specialist, you may find it helpful to ask:
- Can you confirm that nothing I did during pregnancy caused this?
- What is the recurrence risk for future pregnancies?
- Is there any genetic testing that would be useful for our family?
- Are there other parents of children with Poland anomaly you can connect us with?
Most specialists who work with Poland anomaly are accustomed to these questions and will address them directly. If you are having difficulty finding a specialist with Poland anomaly experience, our provider directory can help.