By: Alaina Pyle, MD, FAAP
Every year in the U.S., some 120,000 babies are born with
congenital disorders. A small number of these infants have genetic differences that can cause serious health outcomes and, in some cases, limit their lives to a few days or weeks.
This article explains what happens when babies are born with extra copies of a specific chromosome, a condition known as
trisomy. If your infant has this condition—or prenatal tests suggest they might—here's what you need to know.
What is trisomy?
Humans have 26 pairs of chromosomes inside every cell in their bodies. Pairs are formed during conception, when egg and sperm cells come together. One chromosome comes from the mother and one from the father, making matched pairs totaling 46 chromosomes in all.
Babies born with trisomy have an extra copy of one chromosome. This gives them 3 chromosomes instead of 2 in a particular DNA location.
Types of trisomy disorders
The most common form of trisomy is
Down syndrome, also known as trisomy 21. Two less common trisomy disorders are trisomy 13 (also called Patau syndrome) and trisomy 18 (Edwards syndrome). Health effects of trisomy 13 & trisomy 18
Compared with Down syndrome, trisomy 13 and trisomy 18 have a much more serious impact on an infant's health. These conditions affect nearly every organ in a baby's body, which is why most survive only a few days or weeks. Miscarriage rates in these cases are higher than those for pregnancies where trisomy is not present. Babies who survive will all have lifelong, significant limitations in their development (problems with walking, talking, feeding themselves, etc.).
There is some good news, too. Thanks to progress in medical treatments and surgeries such as heart repair, some children with trisomy 13 and 18 are living longer—and a small number live into their teens and 20s. That said, it's important to understand the issues your child might face.
Babies born with trisomy 13 often have:
Low birth weight
Small heads with sloping foreheads; brain structure differences that affect speech, learning and more
Close-set eyes, often with eye problems; low-set, unusually shaped ears; underdeveloped nostrils
Extra fingers or toes; unusually shaped feet
Purplish-red birthmarks
Heart and kidney defects
Problems with breathing, sometimes requiring a breathing tube long-term
Problems with feeding, usually needing a feeding tube long-term
Internal organs that hang outside the body; other problems with different organs
Babies born with trisomy 18 may have some of the same issues.
Nearly 90% will have heart defects. Trisomy 18 can also make babies frail and thin. Other common problems:
Small mouth and jaw; cleft lip or palate; weak cry
Clenched fists with fingers that won't extend
Brain structure differences that affect speech, learning and more
Problems with breathing, sometimes requiring a breathing tube long-term
Problems with feeding, usually needing a feeding tube long-term
High blood pressure; kidney problems; other problems with different organs
Seizures
Hearing loss
Spina bifida (part of the spinal cord exposed)
Scoliosis (curved spine)
How are trisomy 13 & trisomy 18 diagnosed?
Both conditions can usually be diagnosed before babies are born. An infant's DNA can be tested using samples of the mother's blood or the fluid in her uterus (amniotic fluid).
After birth, medical teams can often make an initial diagnosis based on the baby's appearance and health struggles. DNA tests can then be used to confirm trisomy 13 or 18 to help guide treatment.
Did I do something to cause trisomy 13 or 18 in my child?
Trisomy 13 and 18 are more common among parents aged 35 and older. But all cases are caused by rare genetic mutations that may happen randomly, not something that parents do (or don't do). So if you didn't eat perfectly or exercise during pregnancy, don't be hard on yourself. Though the AAP definitely recommends
healthy choices during pregnancy, your lifestyle did not lead to your child's health problems.
Also keep in mind that trisomy 13 and 18 do not
run in families, the way that cancer, heart disease and other maladies can. Even though trisomy has a genetic cause, it is not passed down through your family tree.
Following trisomy diagnosis, how will my baby be treated?
Babies with trisomy 13 or 18 generally receive care in the hospital's neonatal intensive care unit (NICU) unless a family has lovingly chosen to focus on comfort care, with the baby usually staying with mom after birth. Treatment will depend on your child's condition and specific health challenges. Surgery may be considered to correct life-threatening issues such as heart defects. Your medical team will continue to work with you to create a plan that supports your baby and aligns with your values and wishes.
AAP policy explained: trisomy guidance for timely, compassionate care
The American Academy of Pediatrics (AAP) recently updated its guidance to help medical professionals and families navigate the challenges of trisomy 13 and 18. Among recommendations:
Medical teams should inform parents that their child's lifespan will be significantly affected. At present, only 5% to 15% babies with trisomy 13 or 18 live long enough to celebrate their first birthday. Babies who survive will have serious problems with movement, language, learning and more. Despite growing hope for longer lives, there are lingering ethical and moral controversies surrounding care for trisomy 13 and 18. (These concerns often rise up whenever someone's life expectancy is short and extensive medical care is needed.)
Medical teams should work closely with families, ideally before the child is born, to follow an informed decision-making process for loving parents to make choices for their child. This can include admission to a NICU and medical procedures, or can include supportive care that protects the child from invasive procedures. Whenever possible, infants diagnosed with trisomy 13 or 18 before birth should be delivered in hospitals equipped to offer timely, effective care that matches their families' goals of care.
Parents and caregivers deserve transparency and compassionate support in making choices for their children. Withholding life-extending care from newborns with trisomy 13 or 18 can only be justified when parents decide this is the course they want to take. In these cases, comfort care is a reasonable pathway that many loving parents choose.
When your baby has a life-limiting condition: where to turn for understanding & support
Learning that your little one has a serious, life-limiting health condition can be devastating. Many parents struggle with feelings of anger, frustration and hopelessness—not to mention the long days and nights learning how to care for a fragile infant.
Without support, your own physical and mental health can suffer. Get the care you need as early as you can. Rely on your family doctor and pediatrician for resources that help parents of seriously ill children. Support groups,
grief counseling resources can make all the difference in helping you feel calm and prepared.
More information
About Dr. Pyle
 Alaina Pyle, MD, FAAP, is an Assistant Professor of Neonatal-Perinatal Medicine in the Department of Pediatrics at University of Connecticut Medical School and Connecticut Children's. Dr. Pyle's work focuses on shared decision-making processes, particularly for infants with complex and life-limiting diagnoses. Dr. Pyle is a co-author of the AAP clinical report "Guidance for Caring for Infants and Children With Trisomy 13 and Trisomy 18."
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