Information on Trisomy 13

Dr. Greene's Answer

Melissa, one of my most vivid memories from my pediatric residency was sitting with a mom while she rocked her son who was born with trisomy 13. We were in the Intensive Care Nursery at Children’s Hospital Oakland, surrounded by tiny premature babies in incubators. This boy was full term and normal size. While the other babies were all hooked up to mechanical ventilators, IV pumps, or other high tech equipment, this child was simply wrapped in a receiving blanket, cradled in his mother’s arms. As she gently rocked back and forth in the plain wooden chair, she knew that he would die within a day.

The fullness of motherhood was compressed into that day. A mother’s deep love for her son, her tender concern, her exquisite pain of separation, her comforting touch for a lifetime’s scraped knees, her worry for a lifetime’s dangers, her peace in their inseparable bond, all came together in that rich moment as she gazed upon her precious little boy.

Even when our children have normal life-spans, their childhoods vanish oh so quickly. When childhood is cut short, it is a gut-wrenching shock. Trisomy 13 (also called Patau Syndrome) occurs in up to 1 out of 5,000 newborns (Smith’s Recognizable Patterns of Human Malformation, Saunders 1988). Even the mildest forms of this syndrome can be devastating.

The 13th chromosome contains blueprints that direct a baby’s development in the early weeks following conception. When a child has an extra 13th chromosome (three copies, instead of two), as is the case in trisomy 13, the genetic messages are confused and contradictory – there’s just too much to juggle. This results in multiple significant defects in major organ systems. The brain is often the most severely affected. Children with trisomy 13 may also have abnormalities in the shape of their lips, eyes, ears, fingers, toes, and bones. It’s also common for these children to be born blind, deaf, and with no sense of smell. Taste and touch become the limited means by which a mother can convey an ocean of feeling.

Most children with trisomy 13 have some kind of heart defect, but a double-outlet right ventricle is not common. A normal heart has four chambers. Blood from the body enters the right atrium. From there, it flows into the right ventricle, whose strong muscular wall sends the blood out of the heart to the lungs (via the pulmonary artery). In the lungs, the blood is supplied with oxygen before it returns to the heart, entering the left atrium. From there, it flows into the left ventricle, whose mighty walls propel the blood out of the heart (via the aorta) to supply the rest of the body with oxygen.

In double-outlet right ventricle, the pulmonary artery and aorta both exit from the right ventricle. Thus, poorly oxygenated blood is used for the body’s main supply. The only exit from the left ventricle is a hole in the wall (called a ventricular septal defect) through which the oxygenated blood from the lungs can at least enter the right ventricle to blend with the depleted blood from the body before it leaves. In your son, a hole in the wall between the two atria (an atrial septal defect) also allowed mixing of the blood entering the heart. Double-outlet right ventricle occurs in less than 1 percent of children with congenital heart disease.

Trisomy 13 was first described in 1657, but four hundred fifty years of medical knowledge have not improved the outlook for children born with this syndrome. Most babies who are conceived with trisomy 13 die early in gestation. Of the babies who live to be born, about 44% die within the first month and 69% die by six months. Only 18 percent reach their first birthdays — and these have severe mental defects and seizures (Smith’s Recognizable Patterns of Human Malformation, Saunders 1988).

While we cannot cure trisomy 13, we have started to find ways to detect it early. Sometimes, a blood test, called the AFP (alphafetoprotein) or triple screen, may help a pregnant woman find out her baby’s risk of several diseases, including Trisomy 13. Trisomy 13 is often detectable on prenatal ultrasound as early as 10 weeks of pregnancy. Chorionic villous sampling can detect trisomy 13 by 12 weeks. Amniocentesis, usually performed after 16 weeks gestation, can give a definite answer if any question still remains.

Often, trisomy 13 is associated with older mothers. Even so, the risk of having another baby with trisomy 13 is usually very low — unless, as with your son, the trisomy 13 is a translocation. A translocation is not associated with mom’s age, but is a hereditary chromosome problem. The risk of recurrence in some types of (balanced) translocations can be quite high. The inheritance of trisomy 13 is very complex. By testing your blood and that of the baby’s father, a geneticist can give you the best available information for your situation.

Trisomy 13 is a desolate and difficult challenge that I wish you didn’t have to face. Melissa, your mother’s heart comes through in your search for information about your son. You are a mother in the fullest sense of the word.