by Alan Greene, MD, FAAP
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 are 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, 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. It's also not unusual 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 uncommon. 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).
The farthest we've advanced is in the development of early detection. Trisomy 13 is often detectable on ultrasound as early as 10 weeks. 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.