Bicuspid aortic valve is not inherited specifically from either mother or father. The condition follows an autosomal dominant pattern, meaning the relevant gene variants sit on non-sex chromosomes and can be passed equally by either parent. Despite this, BAV shows a striking male predominance and a complicated genetic architecture that makes the inheritance picture far less straightforward than a simple “one parent gives it to you” story.
What Autosomal Dominant Actually Means for Families
The genes most strongly linked to bicuspid aortic valve are located on autosomes, the 22 pairs of chromosomes that are the same regardless of sex. Because BAV follows an autosomal dominant inheritance pattern, a single copy of a variant gene from one parent is theoretically enough to cause the condition.1PubMed Central. Genetics in bicuspid aortic valve disease: Where are we? That parent could be the mother or the father with equal probability.
Here is the catch: the condition shows “incomplete penetrance,” which means that carrying a BAV-related gene variant does not guarantee you develop a bicuspid valve. A parent can carry the variant and have a perfectly normal three-leaflet aortic valve, then pass the variant to a child who ends up with BAV. This makes the condition seem to skip generations or appear randomly in a family, even though it is following a genetic trail.2PubMed Central. Bicuspid Aortic Valve: Genetic and Clinical Insights On top of incomplete penetrance, BAV has “variable expressivity,” meaning two family members who both carry the same variant can look very different clinically. One might have a mildly abnormal valve that never causes symptoms, while another develops significant valve disease or an enlarged aorta.
How Heritable Is BAV, Really?
One of the earliest and most frequently cited family studies estimated the heritability of BAV at roughly 89%, a strikingly high figure that placed it among the most heritable cardiovascular conditions.3PubMed. Bicuspid aortic valve is heritable A later study of families found a lower but still very significant heritability of about 47%, reinforcing that genetics play a major role even if the exact magnitude is debated.4PubMed. Familial clustering of bicuspid aortic valve and its relationship with aortic dilation in first-degree relatives The gap between these estimates likely reflects differences in how the studies were designed and which populations they examined, but the direction is consistent: BAV clusters in families far more than chance would predict.
That said, most individual cases of BAV are considered sporadic, meaning the person has no obvious family history. Familial clustering shows up in roughly 30 to 40% of cases.5European Heart Journal. Maternal pre-existing and gestational diabetes and the risk of bicuspid aortic valve in the offspring The rest appear to arise from new mutations, from combinations of low-risk gene variants adding up, or from environmental factors during fetal development that we do not yet fully understand. So a person diagnosed with BAV who has no affected relatives is the norm, not the exception.
The Genes Researchers Have Found So Far
The single most studied gene in BAV is NOTCH1, which plays a role in how cells in the developing heart communicate during the formation of valve tissue. Variants in NOTCH1 were the first to be linked to familial BAV, and they tend to cluster in families that also have other left-sided heart problems. But NOTCH1 variants explain only about 2% of familial BAV cases and less than one-tenth of a percent of sporadic cases, which means the vast majority of BAV has nothing to do with this gene.6PubMed Central. Contribution of NOTCH1 genetic variants to bicuspid aortic valve and other congenital lesions Incomplete penetrance was observed in nearly half of the families with confirmed harmful NOTCH1 mutations, underscoring why even a known genetic cause does not reliably predict who in a family will be affected.
Beyond NOTCH1, researchers have identified rare harmful variants in genes like GATA4, SMAD6, and ROBO4. In one study of patients who developed BAV complications early in life, about 18% carried rare variants in one of these genes.7PubMed Central. Rare deleterious variants of NOTCH1, GATA4, SMAD6, and ROBO4 are enriched in BAV with early onset complications but not in BAV with heritable thoracic aortic disease These genes are involved in valve formation during early embryonic development, and again, they sit on autosomes, not on the X or Y chromosome. Animal models have identified additional candidates: variations in HOXA1, for instance, cause BAV in mice by disrupting the migration of neural crest cells into the developing valve.8Nature Communications. Variations in the poly-histidine repeat motif of HOXA1 contribute to bicuspid aortic valve in mouse and zebrafish
The overall picture is one of many genes contributing small amounts of risk rather than one master gene driving the condition. Genetic testing for BAV-related aortopathy currently has a diagnostic yield of only about 5%, meaning 19 out of 20 people tested will not get a definitive genetic answer.9European Journal of Preventive Cardiology. Indications and utility of cardiac genetic testing in athletes
Polygenic Risk and What It Changes
A large genome-wide study brought the genetics of BAV into sharper focus. Researchers constructed a polygenic risk score, essentially a tally of many common genetic variants each contributing a small amount of risk, and found that people in the highest range of this score had roughly double the odds of having BAV compared to those in the lowest range.10PubMed. Genome and Transcriptome-Wide Analyses Identify Multiple Candidate Genes and a Significant Polygenic Contribution in Bicuspid Aortic Valve The score was also linked to a higher risk of thoracic aortic aneurysm and atrial fibrillation, suggesting these conditions share some genetic underpinnings with BAV.
This matters because it shifts the conceptual model. Rather than BAV being a condition where one broken gene causes the problem, most cases likely result from dozens or hundreds of common variants that each nudge the developing valve slightly off course. Both parents contribute roughly half of these common variants. There is no parent-of-origin effect built into this polygenic architecture: the mother’s contribution and the father’s contribution carry the same statistical weight.
Why Is BAV So Much More Common in Males?
If BAV is autosomal and both parents contribute equally, the obvious question is why males are affected far more often. In a large newborn screening study in Copenhagen, BAV turned up in about 0.77% of all newborns, with a male-to-female ratio of roughly 2 to 1.11PubMed Central. Prevalence of Bicuspid Aortic Valve and Associated Aortopathy in Newborns in Copenhagen, Denmark Other estimates put the ratio even higher, at three to four times more frequent in men than in women.12PubMed. Sex differences in bicuspid aortic valve disease
The leading hypothesis for this disparity involves the X chromosome. Women carry two copies of the X chromosome; men carry only one. If genes on the X chromosome play a protective role in valve development, women would get a double dose of that protection while men would get only a single dose. This is not the same as X-linked inheritance in the traditional sense: the main BAV-causing variants are still on autosomes. But modifier genes on the X chromosome could raise the threshold for developing a visible valve defect, meaning women would need a stronger push from autosomal risk variants before the valve actually forms abnormally.
Turner syndrome provides a natural test of this idea. Women with Turner syndrome are missing all or part of one X chromosome, effectively leaving them with an X-chromosome dosage similar to males. BAV prevalence in these women is dramatically elevated. In one study of women with complete loss of one X chromosome, about 34% had a bicuspid aortic valve, a prevalence roughly 40 to 50 times higher than the general female population.13PubMed. Bicuspid aortic valve and aortic coarctation are linked to deletion of the X chromosome short arm in Turner syndrome Researchers narrowed the critical region to the short arm of the X chromosome, where a gene called TIMP1 drew particular attention: having only one copy of TIMP1 appeared to increase the odds of developing BAV-related aortic disease.14PubMed Central. The genetic basis of Turner syndrome aortopathy
One study specifically tested whether genomic imprinting, a phenomenon where it matters which parent a gene came from, played a role in the high BAV rate in Turner syndrome. It found no clear evidence that the parental origin of the remaining X chromosome influenced BAV development.15European Heart Journal. The contribution of X-chromosome genomic imprinting to the bicuspid aortic valve and aortic coarctation prevalence in women with Turner syndrome In other words, it did not seem to matter whether the X chromosome came from the mother or the father, which further supports the idea that this is about gene dosage rather than parent-of-origin effects.
How BAV Forms During Fetal Development
To understand why inheritance is so hard to predict, it helps to know a little about how the aortic valve is built. The valve forms during the first weeks of embryonic heart development from structures called valve cushions. These cushions are shaped by at least three interacting cellular processes: the transformation of cells lining the heart into the tissue that fills the cushions, the behavior of neural crest cells migrating into the outflow tract, and the maturation of cushion cells into the specialized tissue of the final valve leaflets.16PubMed. Embryonic development of bicuspid aortic valves A disruption in any of these steps, driven by different genes or combinations of genes, can result in two leaflets fusing into one, producing a bicuspid valve.
This explains why so many different genes can lead to the same end result. NOTCH1 influences cell communication during cushion formation. GATA4 regulates early cardiac development broadly. HOXA1 affects neural crest migration. They converge on the same developmental bottleneck from different directions, which is why genetic testing for any single gene comes back negative in most patients.
BAV and the Aorta Share a Genetic Thread
One finding that sometimes confuses families is that BAV and thoracic aortic aneurysm appear to share genetic roots. A person with BAV is at higher risk of developing an enlarged aorta, and family members who do not have BAV themselves can still develop aortic dilation. Research suggests a shared but diverse underlying genetic cause linking BAV and thoracic aortic aneurysm across three overlapping patient groups: those with BAV alone, those with an aneurysm alone, and those with both.17PubMed Central. Bicuspid aortic valve and thoracic aortic aneurysm: three patient populations, two disease phenotypes, and one shared genotype
Aorta measurements themselves are heritable even after accounting for body size, sex, and age, and this heritability appears to be separate from whatever causes BAV.18Frontiers in Genetics. Aorta Measurements are Heritable and Influenced by Bicuspid Aortic Valve So a family may carry genetic variants that affect both the valve and the aortic wall, but those effects can segregate independently. This is why guidelines recommend screening not just for BAV itself in relatives, but also for aortic dilation.
Should Your Family Be Screened?
Current guidelines recommend that first-degree relatives of anyone diagnosed with BAV, meaning parents, siblings, and children, undergo echocardiographic screening. A study of this approach in a pediatric cardiology setting found that the prevalence of BAV among first-degree relatives was consistent with what larger prospective adult studies have reported, supporting the usefulness of screening in everyday clinical practice.19PubMed. First-Degree Relatives Screening of Patients with Bicuspid Aortic Valve: Effectiveness and Feasibility in Pediatric Cardiology Daily Practice
Screening matters because BAV can be completely silent for decades. Many people learn they have it only when a heart murmur is detected incidentally or when valve disease develops in middle age. Because incomplete penetrance means an affected parent might not know they carry the variant, screening siblings and children of a known BAV patient casts a wider net than waiting for symptoms. An echocardiogram, a painless ultrasound of the heart, is the standard tool and carries no risk.
For families with multiple members affected by BAV or associated aortic disease, a referral to a genetics specialist can help map the pattern of inheritance and determine whether genetic testing is worthwhile. Given the low diagnostic yield of current panels, testing is most informative when BAV appears alongside other congenital heart defects or connective tissue features, rather than in isolated cases.
How BAV Looks Different in Men and Women
The sex imbalance in BAV is not limited to who gets it. Among people who do have BAV, the clinical presentation differs between men and women. In a large international registry of nearly 2,000 BAV patients, men were more likely to present with significant aortic regurgitation, where the valve leaks backward, while women more often presented with aortic stenosis, where the valve narrows and restricts forward flow.20PubMed. Sex Differences in Phenotypes of Bicuspid Aortic Valve and Aortopathy: Insights From a Large Multicenter, International Registry These differences affect when and how the condition is detected, and they can influence treatment timing and surgical strategy.
Women with BAV also tend to be diagnosed later than men, partly because the condition is less expected in women and partly because the leaking-valve pattern that is more common in men may produce a more noticeable murmur earlier in life. For families wondering whether a daughter is “safe” because BAV runs more often in males, the answer is no. The risk is lower but not absent, and the disease can present differently, which makes screening all first-degree relatives regardless of sex the more cautious approach.
Environmental Factors During Pregnancy
Because most BAV cases are sporadic, researchers have looked beyond pure genetics for contributing factors. Maternal diabetes during pregnancy has drawn attention as a potential risk modifier. A study examining this link found that familial clustering explains only part of the picture and proposed that the overall cause is likely multifactorial.5European Heart Journal. Maternal pre-existing and gestational diabetes and the risk of bicuspid aortic valve in the offspring This is an active area of research, and the evidence is not yet strong enough to point to specific environmental exposures that parents could meaningfully control. But it underscores that BAV is not purely a genetic coin flip. Fetal development involves a complex interaction between the genetic blueprint and the intrauterine environment, and disruptions from either side can contribute.
For parents who already have a child with BAV and are planning another pregnancy, the recurrence risk is real but hard to pin down precisely. Estimates vary depending on which family members are affected and whether the underlying genetic variant has been identified. Genetic counseling before or during pregnancy can help families understand their individual risk profile, even if a specific gene cannot always be named.