context: It can be extremely difficult to hear that your unborn baby has trisomy 13, also known as Patau Syndrome. You probably have a lot of questions about what caused it and whether or not it can be treated. But it's better that you know everything you can about this chromosomal disorder as early in your pregnancy as possible. That way you can discuss all of your options with your doctor and determine what's best for you and your baby. Trisomy 13 is a genetic disorder that your baby gets when she has an extra 13th chromosome. In other words, she has three copies of her chromosome 13 when she should have just two. It happens when cells divide abnormally during reproduction, and create extra genetic material on chromosome 13. The additional chromosome can come from either the egg or the sperm, but doctors think that the chances a woman will have a baby with any chromosome abnormality go up after age 35. The extra 13th chromosome causes severe mental and physical problems. Unfortunately, most babies born with it don't live past their first month or year. But some can survive for years. That's because there are two different kinds of trisomy 13. Babies can have three copies of chromosome number 13 in all of their cells, or in only some of them. The symptoms depend on how many cells have the extra chromosome. Your doctor might spot physical signs of trisomy 13 during your routine first-trimester fetal ultrasounds. Or it could show up in tests such as cell-free DNA screening ( NIPT) or the PAPP- A (pregnancy-associated plasma protein A). These are all screening tests, which means they can't tell your doctor whether your baby definitely has trisomy 13. They only alert your doctor that your baby is more likely to have trisomy 13, and that you need more tests to confirm it. Your doctor likely will recommend you have a chorionic villus sampling ( CVS) or amniocentesis to be 100% certain. Babies born with trisomy 13 often have a low birthweight, even if they are not born before the due date. They usually have brain-structure problems, which can affect their facial development, as well. A baby with trisomy 13 may have eyes set close together and an underdeveloped nose or nostrils. Other birth defects of trisomy 13 include: Clenched hands Cleft lip or palate Extra fingers or toes (polydactyly) Hernias Kidney, wrist, or scalp problems Low-set ears Small head (microcephaly) Undescended testes Babies born with trisomy 13 can have many health problems, and more than 80% don't survive more than a few weeks. Those that do can have serious complications including: Breathing difficulties Congenital heart defects Hearing loss High blood pressure (hypertension) Intellectual disabilities Neurological problems Pneumonia Seizures Slow growth Trouble feeding or digesting food There is no cure for trisomy 13, and treatments focus on your baby's symptoms. These can include surgery and therapy. Although, depending on the severity of your baby's issues, some doctors may choose to wait and consider any measures based on the chances of your baby's survival. Trisomy 13 isn't always fatal. But doctors can't predict how long a baby might live if she doesn't have any immediate life-threatening problems. However, babies born with trisomy 13 rarely live into their teens.