Patau Syndrome (Trisomy 13)

Patau’s syndrome (trisomy 13) is a rare chromosomal condition caused by an extra copy of chromosome 13, occurring in approximately 1 in 5,000 live births.

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What is Patau Syndrome? Key Information for Expecting Parents

Patau syndrome, also known as trisomy 13, is a rare chromosomal condition caused by an extra copy of chromosome 13. This additional genetic material disrupts normal fetal development. It leads to serious physical and intellectual disabilities. The condition affects multiple organ systems and unfortunately carries a poor prognosis. Most affected babies do not survive beyond their first year of life.

What is Patau syndrome?

Patau's syndrome (trisomy 13) is a rare chromosomal condition caused by an extra copy of chromosome 13, occurring in approximately 1 in 5,000 live births.

During pregnancy, Patau syndrome can be detected through routine NHS screening programmes and specialised diagnostic tests. Early detection through anomaly scans and non-invasive prenatal testing (NIPT) allows families to make informed decisions about their pregnancy. Genetic counselling services provide essential support and information about the condition, helping expectant parents understand their options and access appropriate screening tests throughout their pregnancy journey.

Patau syndrome can be detected through various screening and diagnostic methods. Initial screening includes the NHS combined test (blood test and nuchal scan) between 11-14 weeks, followed by the anomaly scan at 18-20 weeks. If screening suggests increased risk, diagnostic tests such as amniocentesis or chorionic villus sampling (CVS) can provide definitive confirmation through chromosome analysis.

Patau Syndrome: Key Statistics

1 in 5,000 Patau syndrome occurs in approximately 1 in 5,000 live births, making it one of the more common chromosomal conditions (NCBI StatPearls)

1 in 5,000 The condition occurs in approximately 1 in 5,000 live births, though many affected pregnancies result in miscarriage (NCBI StatPearls)

The sex ratio at birth is slightly skewed towards females, presumably due to decreased survival amongst males

95% Most cases (approximately 95%) result from random chromosomal changes in healthy parents and are not inherited

Preterm Pregnancies affected by Patau syndrome are considerably more likely to deliver preterm (before 37 weeks’ gestation)

The condition is caused by an extra copy of chromosome 13 (trisomy 13) in each cell

18–20 weeks The NHS mid-pregnancy anomaly scan is offered to all pregnant women between 18+0 and 20+6 weeks as part of the Fetal Anomaly Screening Programme

1 in 150 A cut-off risk of 1 in 150 is used by NHS trusts to identify higher-chance results requiring further investigation

Patau Syndrome Testing and Support Options

Non-Invasive Prenatal Testing (NIPT)

Advanced NIPT screening is available from as early as 10 weeks of pregnancy to assess the risk of Patau syndrome. This blood test analyses fetal DNA circulating in maternal blood to evaluate chromosomal conditions including trisomy 13. The test demonstrates high accuracy for detecting Patau syndrome, providing early information about pregnancy health.

Multiple NIPT options exist including SMART Test NIPT and PrenatalSAFE NIPT, allowing selection of the most appropriate screening approach. Results are typically available within 7-10 working days, and genetic counselling is available to discuss findings and potential next steps.

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Detailed Anomaly Scanning

Comprehensive anomaly scans can identify physical features associated with Patau syndrome through detailed ultrasound examination. These assessments evaluate fetal development and structural abnormalities that may indicate chromosomal conditions. The heart, brain, kidneys, limbs, and facial features are examined with particular attention to markers associated with trisomy 13.

When concerning features are identified, immediate support is available and urgent referrals for further testing can be arranged. Specialised fetal echocardiography offers detailed heart scanning, as cardiac abnormalities are commonly associated with Patau syndrome and require expert evaluation.

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Genetic Counselling Services

Comprehensive genetic counselling is available for families facing a potential or confirmed Patau syndrome diagnosis. Pre-test counselling helps explain screening options, risk assessment, and implications of different test results. Following any positive screening results, detailed post-test counselling discusses diagnostic options, prognosis, and support resources. Counselling sessions can be arranged in-person or through online genetic counselling services, ensuring accessible support when needed. Close coordination with NHS fetal medicine centres ensures comprehensive support throughout the pregnancy journey.

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Diagnostic Testing Coordination

When screening tests indicate increased risk for Patau syndrome, diagnostic testing coordination includes amniocentesis and chorionic villus sampling (CVS). These definitive tests involve taking a small sample of fetal cells for chromosomal analysis, providing conclusive diagnosis. Collaboration with leading NHS and private laboratories ensures accurate, timely results.

Comprehensive pre-procedure counselling explains the benefits and risks of diagnostic testing. Following procedures, ongoing support is available and immediate follow-up appointments can be arranged to discuss results and coordinate any necessary specialist referrals or additional care requirements.

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Early Pregnancy Assessment

Nuchal translucency scans performed between 11-14 weeks can identify increased risk for chromosomal conditions including Patau syndrome. This early assessment measures fluid collection at the back of the baby’s neck and evaluates other early markers. Combined with maternal blood screening, this provides valuable risk assessment information. Early pregnancy scans are available to establish accurate dating and monitor early development. Accurate pregnancy dating is essential for optimal timing of screening tests and ensures results are interpreted correctly within appropriate gestational age parameters.

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Multidisciplinary Care Coordination

When Patau syndrome is diagnosed, coordination with NHS fetal medicine centres and specialist paediatric teams provides comprehensive care. This includes arranging specialist consultations with neonatologists, paediatric cardiologists, and palliative care teams as appropriate. Seamless communication between all healthcare providers involved in care is facilitated.

Strong relationships with support organisations enable provision of information about local and national resources for families affected by Patau syndrome. Both medical and emotional support needs are addressed throughout the pregnancy and beyond, recognising the significant impact of this diagnosis.

Ultrasound signs of Patau Syndrome during pregnancy

Fetal anomalies linked to Patau syndrome may include physical features affecting different organs and systems. These structural abnormalities often involve the central nervous system, heart, kidneys, and facial development, and can be detected during routine pregnancy scans.

Fetal signs of Patau syndrome called soft markers or anatomical variants, are minor physical features occasionally detected during prenatal scans. While they are not structural anomalies, their presence might slightly raise the statistical likelihood of chromosomal conditions like trisomy 13.

When healthcare providers assess these findings they may consider additional testing. Tests like chorionic villus sampling (CVS) or amniocentesis may be needed for chromosomal analysis, while detailed ultrasound and maternal serum AFP screening are used for neural tube defects.

Holoprosencephaly

A severe brain malformation where the cerebral hemispheres fail to separate properly during early development. This appears on ultrasound as abnormal brain structure with absent or incomplete division between the left and right sides of the brain.

Cardiac defects

Complex congenital heart defects are commonly present in babies with Patau syndrome. These may include septal defects, hypoplastic left heart syndrome, or other structural heart abnormalities visible during fetal echocardiography.

Cleft lip and palate

Bilateral cleft lip and palate are commonly associated with Patau syndrome and can be detected during routine anomaly scans. The facial profile may show characteristic features including a small head (microcephaly) and low-set ears.

Polydactyly

Extra fingers or toes are frequently seen in Patau syndrome, particularly involving the hands. This can be detected during detailed ultrasound examination of the fetal limbs and digits during the second trimester anomaly scan.

Renal abnormalities

Kidney defects including polycystic kidneys or absent kidneys may be detected during pregnancy scans. These abnormalities can affect amniotic fluid levels and may be associated with growth restriction.

Omphalocele

A condition where abdominal organs protrude outside the body through the umbilical cord. This abdominal wall defect appears on ultrasound as organs located outside the normal abdominal cavity.

Growth restriction

Intrauterine growth restriction (IUGR) is commonly associated with Patau syndrome, where the baby measures smaller than expected for gestational age. This may be detected through serial growth scans and estimated fetal weight calculations.

Neural tube defects

Spinal abnormalities including spina bifida may occur in association with Patau syndrome. These defects in neural tube closure can be detected during detailed spinal examination on anomaly scanning.

Your questions answered

What is Patau syndrome?

Patau syndrome, also known as trisomy 13, is a chromosomal condition caused by an extra copy of chromosome 13 in each cell. This additional genetic material disrupts normal development, leading to multiple birth defects and developmental delays. The condition affects approximately 1 in 5,000 pregnancies, though many affected pregnancies result in miscarriage.

What causes Patau syndrome?

The vast majority of Patau syndrome cases (approximately 95%) result from a random error during cell division when eggs or sperm are formed. This error, called nondisjunction, leads to an extra copy of chromosome 13. Most cases are not inherited and occur in pregnancies to healthy parents with no family history of the condition. Advanced maternal age slightly increases the risk, but babies with Patau syndrome can be born to mothers of any age.

How is Patau syndrome diagnosed during pregnancy?

Patau syndrome can be identified through a combination of screening and diagnostic tests during pregnancy. Initial NHS screening includes the combined test (a blood test and nuchal scan) between 11 and 14 weeks, followed by the anomaly scan at 18 to 20 weeks. Non-invasive prenatal testing (NIPT) can also assess the risk from as early as 10 weeks.

If screening suggests an increased chance, diagnostic tests such as amniocentesis or chorionic villus sampling (CVS) can provide definitive confirmation through chromosome analysis. Your healthcare team can explain which tests are most appropriate for your circumstances.

What is NIPT and how accurate is it for Patau syndrome?

Non-invasive prenatal testing (NIPT) is a highly accurate blood test that analyses fetal DNA circulating in the mother’s blood. For Patau syndrome (trisomy 13), NIPT has a detection rate (sensitivity) of around 97% with a very low false-positive rate (specificity approximately 99.

9%); the confidence interval for trisomy 13 is wider than for Down’s syndrome (Taylor-Phillips et al., 2016). NIPT remains a screening test, not a diagnostic one, so a higher-chance result should be confirmed by diagnostic testing.

It is available free on the NHS for women with higher-chance screening results and can help inform decisions about whether to proceed with diagnostic testing.

What are the main physical features of Patau syndrome?

Babies with Patau syndrome typically present with several characteristic features. The severity and combination of features can vary between individuals.

Cleft lip and palate
A small head size (microcephaly) and low-set ears
Extra fingers or toes (polydactyly)
Heart defects and kidney abnormalities
Neural tube defects
Severe intellectual disability

Can Patau syndrome be detected on ultrasound?

Yes, many features of Patau syndrome can be identified during routine ultrasound scans. These may include structural abnormalities such as heart defects, kidney problems, neural tube defects, cleft lip and palate, and growth restriction. However, not all cases will show obvious ultrasound signs, which is why comprehensive screening programmes combine ultrasound with blood tests.

What is the difference between full and partial Patau syndrome?

Full trisomy 13 occurs when there is a complete extra copy of chromosome 13 in every cell, representing about 80% of cases. Partial trisomy 13 involves only part of an extra chromosome 13 and may result in milder symptoms. Mosaic trisomy 13, where only some cells carry the extra chromosome, is the rarest form and typically has the mildest presentation.

What is the prognosis for babies with Patau syndrome?

The prognosis for Patau syndrome is unfortunately poor, with many affected pregnancies ending in miscarriage. Of babies born alive, most have severe disabilities and complex medical needs. Survival rates vary depending on the severity of the abnormalities, but many infants require intensive medical support. Families receive comprehensive support and counselling to help navigate these challenging circumstances.

If I’ve had one baby with Patau syndrome, what’s my recurrence risk?

For most couples, the recurrence risk is very low (less than 1%) because Patau syndrome usually results from random chromosomal errors rather than inherited factors. However, in rare cases involving a chromosomal translocation in one parent, the recurrence risk may be higher. Genetic counselling can provide a personalised risk assessment and discuss options for future pregnancies.

When should I consider genetic counselling?

Genetic counselling is recommended if screening results indicate higher-chance findings, there is a family history of chromosomal conditions, or you are planning a pregnancy after a previous affected pregnancy. Counsellors can explain test results, discuss diagnostic options, and provide emotional support throughout the decision-making process. Many couples find this invaluable for understanding their options and making informed choices.

Are there different types of screening tests available?

Yes, several screening options are available. The NHS offers combined screening (a blood test plus nuchal scan) in the first trimester and quadruple screening in the second trimester. Private clinics may offer additional options such as advanced NIPT panels that screen for multiple conditions simultaneously. Your healthcare provider can discuss which options are most appropriate for your individual circumstances.

Can lifestyle factors influence the risk of Patau syndrome?

No, there are no known lifestyle factors, medications, or environmental exposures that cause or prevent Patau syndrome. The chromosomal error occurs randomly during cell division. Parents should understand that nothing they did or did not do caused the condition. Advanced maternal age is the only recognised risk factor, but even this represents only a slight increase in risk.

What support is available for families affected by Patau syndrome?

Comprehensive support services are available, including specialist medical care, genetic counselling, and psychological support. Many families benefit from connecting with support groups and charities that specialise in chromosomal conditions. Healthcare teams work closely with families to provide coordinated care and ensure access to appropriate resources and support services.

How reliable are screening tests for Patau syndrome?

Screening tests provide risk estimates rather than definitive diagnoses. The combined test is less sensitive for Patau syndrome than for Down’s syndrome, and no combined-test detection rate specific to trisomy 13 is published by NHS screening programmes. NIPT is more sensitive, with a trisomy 13 detection rate of around 97% (Taylor-Phillips et al., 2016), but it remains a screening test rather than a diagnostic one. However, all screening tests can produce false positives and false negatives. Only diagnostic tests such as amniocentesis or CVS can provide definitive confirmation of the condition.

What happens if screening suggests increased risk?

If screening indicates a higher chance, you will be referred to a fetal medicine specialist for detailed counselling and a discussion of your options. These may include further screening with NIPT, diagnostic testing, or additional detailed ultrasound scans. The specialist will explain the implications of the test results and support decision-making that aligns with your individual values and circumstances.

Book NIPT for Rare Diseases

Advanced NIPT screening can assess the risk of Patau syndrome (trisomy 13) and other rare chromosomal conditions from as early as 10 weeks of pregnancy.

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Sources & clinical references

The figures and clinical statements on this page are drawn from the sources below. Guidance evolves — always discuss your individual circumstances with a clinician.

NHS (Genomics Education Programme)Patau syndrome (trisomy 13) | GeNotes Knowledge Hub (NHS Genomics Education Programme)2024
NHSScreening for Down's syndrome, Edwards' syndrome and Patau's syndrome2024
GOV.UK (NHS Fetal Anomaly Screening Programme)Screening for Down's syndrome, Edwards' syndrome and Patau's syndrome2023
PubMed / BMJ OpenAccuracy of non-invasive prenatal testing using cell-free DNA for detection of Down, Edwards and Patau syndromes: a systematic review and meta-analysis (Taylor-Phillips et al., BMJ Open)2016

Early pregnancy scans can detect many major structural fetal anomalies as early as 11–14 weeks (around 46%; Karim et al., 2017)
Learn more about NIPT screening options for chromosomal conditions
The vast majority of Patau syndrome cases (approximately 95%) result from a random error during cell division when forming eggs or sperm. This error, called nondisjunction, leads to an extra copy of chromosome 13. Most cases are not inherited and occur in pregnancies to healthy parents with no family history of the condition. Advanced maternal age slightly increases the risk, but babies with Patau syndrome can be born to mothers of any age.
Non-invasive prenatal testing (NIPT) is a highly accurate blood test that analyses fetal DNA in the mother’s blood. For Patau syndrome (trisomy 13), NIPT has a detection rate (sensitivity) of around 97% with a very low false-positive rate (specificity approximately 99.9%); the confidence interval for trisomy 13 is wider than for Down’s syndrome (Taylor-Phillips et al., 2016). NIPT remains a screening test, not a diagnostic one, so a higher-chance result should be confirmed by diagnostic testing. It is now available free on the NHS for women with higher-chance screening results and can help inform decisions about whether to proceed with diagnostic testing.
Babies with Patau syndrome typically present with multiple characteristic features including cleft lip and palate, small head size (microcephaly), low-set ears, extra fingers or toes (polydactyly), and severe intellectual disability. Heart defects, kidney abnormalities, and neural tube defects are also common. The severity and combination of features can vary between individuals.
Full trisomy 13 occurs when there is a complete extra copy of chromosome 13 in every cell, representing about 80% of cases. Partial trisomy 13 involves only part of an extra chromosome 13 and may result in milder symptoms. Mosaic trisomy 13, where only some cells have the extra chromosome, is the rarest form and typically has the mildest presentation.
The prognosis for Patau syndrome is unfortunately poor, with many affected pregnancies ending in miscarriage. Of babies born alive, most have severe disabilities and complex medical needs. Survival rates vary depending on the severity of abnormalities, but many infants require intensive medical support. Families receive comprehensive support and counselling to help navigate these challenging circumstances.
For most couples, the recurrence risk is very low (less than 1%) because Patau syndrome usually results from random chromosomal errors rather than inherited factors. However, in rare cases involving chromosomal translocations in one parent, the recurrence risk may be higher. Genetic counselling can provide personalised risk assessment and discuss options for future pregnancies.
Genetic counselling is recommended if screening results indicate higher-chance findings, there is a family history of chromosomal conditions, or pregnancy is being planned after a previous affected pregnancy. Counsellors can explain test results, discuss diagnostic options, and provide emotional support throughout the decision-making process. Many couples find this invaluable for understanding their options and making informed choices.
Yes, several screening options are available. The NHS offers combined screening (blood test plus nuchal scan) in the first trimester and quadruple screening in the second trimester. Private clinics may offer additional options such as advanced NIPT panels that screen for multiple conditions simultaneously. Healthcare providers can discuss which options are most appropriate for individual circumstances.
No, there are no known lifestyle factors, medications, or environmental exposures that cause or prevent Patau syndrome. The chromosomal error occurs randomly during cell division. Parents should understand that nothing they did or didn’t do caused the condition. Advanced maternal age is the only recognised risk factor, but even this represents only a slight increase in risk.
Screening tests provide risk estimates rather than definitive diagnoses. The combined test is less sensitive for Patau syndrome than for Down’s syndrome, and no combined-test detection rate specific to trisomy 13 is published by NHS screening programmes. NIPT is more sensitive, with a trisomy 13 detection rate of around 97% (Taylor-Phillips et al., 2016), but it remains a screening test rather than a diagnostic one. However, all screening tests can have false positives and false negatives. Only diagnostic tests such as amniocentesis or CVS can provide definitive confirmation of the condition.
If screening indicates higher risk, referral to a fetal medicine specialist occurs for detailed counselling and discussion of options. These may include further screening with NIPT, diagnostic testing, or additional detailed ultrasound scans. The specialist will explain the implications of test results and support decision-making that aligns with individual values and circumstances.
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