Medically reviewed by Karen Gill, M.D. — Written by Ashley Marcin on February 28, 2022
A baby’s genetic makeup is determined when the sperm meets the egg during fertilization. Typically, a full set of DNA is formed, which contains 23 pairs of chromosomes. Sometimes, extra chromosomes are shared, resulting in what is called a trisomy. Patau syndrome is also known as trisomy 13. It means that a person has an extra copy of chromosome number 13. Keep reading to learn more about what causes this syndrome, what the symptoms are, and what you can expect after diagnosis. Trisomy 13 is a rare genetic disorder that affects around 1 in every 7,409 births in the United States. It is present when there are three copies of chromosome 13 instead of the usual two in each cell in the body. While rare, trisomy 13 is a very serious condition that can cause developmental issues that may lead to miscarriage, stillbirth, or infant death soon after birth. A child who does survive may have a low birth weight and other serious medical issues. VariationsIf there is a complete extra copy of chromosome number 13 in each cell, the condition is called trisomy 13. Sometimes this extra genetic information gets split between chromosome 13 and another chromosome — a translocation. This happens about 10 percent of the time. In about 5 percent of individuals with trisomy 13, the extra copy of chromosome 13 only affects some cells and not all. When this happens, it’s called trisomy 13 mosaicism or partial trisomy 13. For individuals with mosaic trisomy 13, the signs and symptoms are generally less severe, and children may live longer. You may have no symptoms during your pregnancy that indicate your child has Patau syndrome. Your doctor may uncover the first signs after cell-free DNA screening, other prenatal screening tests, or during a routine ultrasound exam. Once your baby is born, you may observe the following features:
Around 80 percent of babies born with trisomy 13 also have congenital heart abnormalities. Some may also have conditions that affect brain development and the kidneys. In most cases, trisomy 13 happens spontaneously soon after the sperm and egg meet. The issue may arise as the reproductive material of either parent divides, or it may happen as cells divide after fertilization itself. In either of these cases, the extra chromosome happens at random. That said, in rare cases, some people may pass a trisomy onto their child if they themselves have what is called a “balanced” translocation. This means that the parent carrier has a set of chromosomes that aren’t the norm but that they are balanced, so they don’t cause medical issues. However, when the parent with the balanced translocation has a child, the genetic information may be passed on and cause a trisomy 13 in the child. Trisomy 13 can be diagnosed while you are pregnant or after your baby is born.
After birth, your child’s doctor may make a diagnosis based on a physical exam, certain characteristics, and blood tests to analyze chromosomes. Treatment for Patau syndrome is often targeted at whatever symptoms a child is experiencing. Instead of curative treatments, medical help tends to be focused on making the child comfortable, since many babies do not live long after birth. Your doctor may assemble a healthcare team to provide care for various health conditions while working together. Treatments may eventually involve surgery — for heart issues, cleft palate or lip, or other conditions — physical therapy, and other medical or social services. Children who live longer may also benefit from early intervention and special education programs as they grow. Since most cases of Patau syndrome happen at random, it’s possible to have a child with this condition even if you have no known risk factors. The primary risk factor mentioned in the medical literature is paternal age. So, as a parent’s age goes up, so does the potential for trisomy 13. Again, the other risk factor is if either parent has a “balanced” translocation. This can be uncovered through genetic testing. Your doctor may also suggest genetic testing if you already have a child with trisomy 13 (or another genetic condition) to determine if there’s an inherited factor at play that may impact future pregnancies. Trisomy 13 is a very serious but very rare condition. About half of all pregnancies involving trisomy 13 will result in pregnancy loss before the 12th week. According to a 2017 study, 84 percent of pregnancies involving trisomy 13 that reach 39 weeks result in a live birth. However, more than 90 percent of infants with trisomy 13 will not survive their first year. Most babies with this rare condition live only 7 to 10 days. Around 5 percent of children with trisomy 13 will live beyond the first year, though they will likely have growth and developmental delays. Some children with trisomy 13 may live longer, but this is extremely rare. Their outlook depends on a number of things, including the type of trisomy they have and associated conditions that have. If your child receives a diagnosis of trisomy 13, you are not alone. This rare syndrome usually has a poor outlook, but there are support groups to help you connect with other families experiencing trisomy 13. Your doctor can also provide local support and other resources you may need along the way. Last medically reviewed on February 28, 2022 Patau's syndrome is a serious rare genetic disorder caused by having an additional copy of chromosome 13 in some or all of the body's cells. It's also called trisomy 13. Each cell normally contains 23 pairs of chromosomes, which carry the genes you inherit from your parents. But a baby with Patau's syndrome has 3 copies of chromosome 13, instead of 2. This severely disrupts normal development and, in many cases, results in miscarriage, stillbirth or the baby dying shortly after birth. Babies with Patau's syndrome grow slowly in the womb and have a low birth weight, along with a number of other serious medical problems. Patau's syndrome affects about 1 in every 5,000 births. The risk of having a baby with the syndrome increases with the mother's age. More than 9 out of 10 children born with Patau's syndrome die during the first year. About 1 in 10 babies with less severe forms of the syndrome, such as partial or mosaic trisomy 13, live for more than a year. Babies with Patau's syndrome can have a wide range of health problems. Their growth in the womb is often restricted, resulting in a low birth weight, and 8 out of 10 will be born with severe heart defects. The brain often does not divide into 2 halves. This is known as holoprosencephaly. When this happens, it can affect facial features and cause defects such as:
Other abnormalities of the face and head include:
Patau's syndrome can also cause other problems, such as:
There may also be abnormalities of the hands and feet, such as extra fingers or toes (polydactyly) and a rounded bottom to the feet, known as rocker-bottom feet. Patau's syndrome happens by chance and is not caused by anything the parents have done. Most cases of the syndrome do not run in families (they're not inherited). They occur randomly during conception, when the sperm and egg combine and the foetus starts to develop. An error occurs when the cells divide, resulting in an additional copy, or part of a copy, of chromosome 13, which severely affects the baby's development in the womb. In many cases, the baby dies before reaching full term (miscarriage) or is dead at birth (stillbirth). In most cases of Patau's syndrome, a baby has a whole extra copy of chromosome number 13 in their body's cells. This is sometimes known as trisomy 13 or simple trisomy 13. In up to 1 in 10 cases of Patau's syndrome, genetic material is rearranged between chromosome 13 and another chromosome. This is called a chromosomal translocation. Patau's syndrome that arises because of this can be inherited. Genetic Alliance UK has more information about chromosome disorders. In a further 1 in 20 cases, only some cells have the extra copy of chromosome 13. This is known as trisomy 13 mosaicism. Occasionally, only part of 1 chromosome 13 is extra (partial trisomy 13). The symptoms and features of both mosaicism and partial trisomy tend to be less severe than in simple trisomy 13, resulting in more babies living longer. You'll be offered a screening test for Patau's syndrome, as well as Down's syndrome (trisomy 21) and Edwards' syndrome (trisomy 18), from 10 to 14 weeks of pregnancy. The test assesses your chances of having a baby with these syndromes. The screening test offered at 10 to 14 weeks of pregnancy is called the combined test because it involves a blood test and an ultrasound scan. If the screening tests show that you have a higher risk of having a baby with Patau's syndrome, you'll be offered a diagnostic test to find out for certain whether your baby has the syndrome. This test will check your baby's chromosomes in a sample of cells taken from him or her. Two techniques can be used to obtain the cell sample: amniocentesis or chorionic villus sampling (CVS). These are invasive tests to remove a sample of tissue or fluid so it can be tested for the presence of the extra copy of chromosome 13. A newer test has recently been developed where a sample of blood from the mother is taken so the baby's DNA found within it can be tested. This is known as non-invasive prenatal testing and is only available privately. If you're not able to have the combined screening test, you'll be offered a scan that looks for physical abnormalities, including those found in Patau's syndrome. This is sometimes called the mid-pregnancy scan and is carried out when you're between 18 and 21 weeks pregnant. Find out more about screening tests in pregnancy There's no specific treatment for Patau's syndrome. As a result of the severe health problems a newborn baby with the syndrome will have, doctors usually focus on minimising discomfort and ensuring the baby is able to feed. For the small number of babies with Patau's syndrome who survive beyond the first few days of life, their care will depend on their specific symptoms and needs. If your baby is diagnosed with Patau's syndrome, either before birth or shortly afterwards, you'll be offered counselling and support. Both parents will need to have their chromosomes analysed if their baby is affected by Patau's syndrome caused by a chromosomal translocation. Genetic testing is carried out to help parents plan for future pregnancies, rather than as part of the decision making process for the current pregnancy. The test results will allow a more accurate assessment to be made of the likelihood of the syndrome affecting future pregnancies. Other family members may also be affected and should be tested. Find out more about genetic testing and counselling Information about your childIf your child has Patau's syndrome, your clinical team will pass information about him or her on to the National Congenital Anomaly and Rare Diseases Registration Service (NCARDRS). This helps scientists look for better ways to prevent and treat this condition. You can opt out of the register at any time. Find out more about the register These organisations are useful further sources of information about Patau's syndrome. They can also provide advice and support:
Page last reviewed: 30 April 2019 |
What is trisomy 13 in pregnancy
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