Trisomy 18 (also known as Edwards Syndrome)
Trisomy 18 is a disorder in which babies are born with 3 copies of chromosome 18 instead of 2. For an unknown reason, this accident occurs at the time of conception and all cells in the body will have this structure. In 90-95% of the children with Trisomy 18 this is the case. In 5-10% of infants with Trisomy 18, only a portion of their cells may contain the extra chromosome 18 (called the mosaic type of Trisomy 18). Infants with Trisomy 18 will be small at birth and have a recognizable appearance caused by the extra chromosome. Some of these features include: prominent back of the head; small eyes, mouth, and jaw; unusual looking ears; clenched fist with overlapping fingers and thumbs; small fingernails; clubbed or rocker bottom soles of the feet; a short breast bone (sternum); and extra skin folds at the back of the neck.
Trisomy 18 occurs at a rate of 1 in 3000-6000 live births. It is somewhat more common as the mother ages but can occur randomly to parents of any age. The majority of babies affected are girls. There is no known cause of Trisomy 18. Studies have shown that only 50% of babies who are carried to term will be born alive. The median of survival among live births has varied between 2.5 and 14.5 days. About 90% - 95% of babies do not survive beyond the first year and many live only a few days.
Common Associated Conditions
Over 90% of infants with Trisomy 18 have a congenital heart defect. The type of heart defect varies, but most would be a ventricular septal defect (opening between the lower heart chambers), an atrial septal defect (opening between the upper chambers), a patent ductus arteriosus (a blood vessel from fetal life that does not close), or a problem with the function of a heart valve. In about 10% of babies the heart defect is extremely severe and life-threatening (hypoplastic left heart, where the main pumping chamber is not formed). Other problems include apnea (the brain does not send a message to the body to breathe), difficulty feeding, under-developed lungs, joint and bone abnormalities (10% of babies), hearing loss (50% of babies), cleft lip (5-10% of babies), and eye defects (10% of babies). Children with this condition are also prone to develop Wilm's tumor (a tumor of the adrenal gland in the abdomen).
Short-term Treatment and Outcomes
Parents of a baby with Trisomy 18 face many difficult decisions regarding the care of their child. Some parents of severely affected infants elect to give comfort care and take their baby home to provide the best and most comfortable circumstances possible. About 10% may survive their first birthdays and enjoy many more years of life with their families and become involved with their community.
Long-term Treatment and Outcomes
Families might choose to have procedures and surgeries to allow their child to live longer with support and improve the child's quality of life. However, this is very rarely an option, because of the severity of the baby's heart defects and other malformations throughout their body. Very small numbers of children can survive as teens and young adults. If they do survive they will require round-the-clock care and life-long home nursing support with activities of daily living. No young adults living with Trisomy 18 are able to live independently.
Babies with Trisomy 18 will be small in size and will grow very slowly even if given good nutrition. They may have difficulty feeding and swallowing and are at risk for recurrent pneumonias and respiratory illnesses from aspirating milk and saliva into their lungs. Seizures, urinary tract infections, delayed development, and profound levels of intellectual disability are also concerns for most babies with this condition.
Implications for Children's Development
The birth of a medically fragile child is very difficult and families will find support from other families who have experienced similar circumstances. Parents often learn from other parents how to be the advocates for their child’s needs. Support groups can be found on the internet as well as in some communities for many of the day-to-day caretaking challenges of parents. Decision-making for children with chromosomal defects is difficult and complex and parents need information and support from their medical providers and community. Listed below are organizations that provide practical information and support for families with a child with trisomy 18.
- Genetics Home Reference: Trisomy 18
- Support Organization for Trisomy 18, 13, and Related Disorders (SOFT)
- Trisomy 18 Foundation
- Hope for Trisomy 13 & 18 - Not-for-profit organization
- Trisomy Conditions
- Prenatal Trisomy Diagnosis Awareness Act Fact Sheet (PDF)