Trisomy 13 (Patau’s syndrome): a guide

Each cell normally contains 23 pairs of chromosomes. In Patau’s syndrome there are three copies of chromosome 13 rather than two. The NHS says this severely disrupts normal development and in many cases ends in miscarriage, stillbirth or the baby dying shortly after birth.

NHS GeNotes, written for clinicians, describes it as a life-limiting genetic condition in which babies born alive have learning disabilities and a wide range of serious health challenges. SOFT UK is the UK charity that supports families affected by trisomy 13 and trisomy 18.

We use both names here because families meet both: trisomy 13 in genetics, and Patau’s syndrome in NHS patient information.

The type of trisomy 13 changes what to expect. The NHS describes four patterns. NHS GeNotes adds that in up to 1 in 10 cases genetic material is rearranged between chromosome 13 and another chromosome.

Growth in the womb is often restricted, so babies tend to have a low birth weight. The NHS says 8 out of 10 are born with severe heart defects. NHS GeNotes puts cardiac anomalies at around 80 percent of cases.

The brain often does not divide into two halves, a condition called holoprosencephaly. The NHS says this can affect the face, with a cleft lip and palate, an abnormally small eye or eyes, or absence of one or both eyes. Other features include a smaller head, ear malformations and deafness.

The NHS also lists abdominal wall defects, kidney cysts, extra fingers or toes and rocker-bottom feet. GeNotes adds that reflux and feeding difficulties are almost universal and that breathing pauses (apnoea) are a leading cause of death in the newborn period.

The NHS says Patau’s syndrome happens randomly when the sperm and egg combine and the baby starts to develop. An error in cell division produces the extra copy of chromosome 13. The chance rises with the mother’s age.

If the cause is a translocation, both parents need chromosome analysis, according to the NHS. The testing is done to help plan future pregnancies, not to decide about the current one, and other relatives may be offered testing. For the usual form, GeNotes says the recurrence risk is low, but a clinical geneticist can give a personal estimate.

The NHS says you will be offered screening for Patau’s, Edwards’ and Down’s syndromes from 10 to 14 weeks of pregnancy. The combined test uses a blood test and an ultrasound scan. If it shows a higher chance, a second screening test called non-invasive prenatal testing (NIPT) is offered. The NHS says it is available free for this purpose.

Only a diagnostic test can confirm the condition. Amniocentesis or chorionic villus sampling takes a sample of cells to check the chromosomes. These tests are invasive. Screening and tests are a choice, and not everyone wants the information. If the combined test is missed, the NHS says a mid-pregnancy scan between 18 and 21 weeks looks for physical differences.

If a baby is diagnosed during pregnancy or shortly after birth, the NHS says parents are offered counselling and support. GeNotes says antenatal care involves a team across midwifery, obstetrics, fetal medicine and paediatrics and that the options of continuing or ending the pregnancy should be discussed with the parents.

There is no specific treatment for Patau’s syndrome, the NHS says. For newborns with severe problems, doctors usually focus on minimising discomfort and ensuring the baby can feed. For the small number who live beyond the first days, care depends on symptoms and needs.

GeNotes says survival time is increased for babies treated intensively, and around 1 in 10 babies with less severe forms such as partial or mosaic trisomy 13 live for more than a year. Decisions about how intensive care should be are made together with parents, often with palliative care teams involved.

Clinical teams pass information to the National Congenital Anomaly and Rare Disease Registration Service, and the NHS says families can opt out at any time.

A diagnosis can feel isolating. SOFT UK says its support line gives a safe, confidential place for anyone whose pregnancy or child is affected by Patau’s or Edwards’ syndrome. The NHS also signposts Genetic Alliance UK and, in its Edwards’ syndrome pages, Antenatal Results and Choices and Bliss for sick or premature babies.

Grief support is part of care. Whatever you decide during pregnancy, there is no single right path, and your midwife or fetal medicine team can arrange counselling.

Screening, fetal medicine, specialist neonatal and palliative care are provided through the NHS. Private providers offer NIPT and genetic counselling, but a higher-chance result usually leads back into NHS fetal medicine for diagnostic testing and planning.

Choose any extra test carefully. Ask what it can and cannot show, what happens if the result is unclear, and who will explain it.