Birth defects research

• The processes of development still hold many mysteries.
• We're working to prevent birth defects and find treatments.
• Sought: genetic and environmental causes of birth defects.

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Heart defects are among the most common birth defects, affecting about 1 in 125 babies in the United States. Advances in diagnosis and surgical treatment have led to dramatic increases in survival for children with serious heart defects. March of Dimes grantees have contributed to these advances. For example, in the 1970s, grantees Abraham M. Rudolph, MD, and Michael A. Heyman, MD, at the University of California at San Francisco, discovered a drug treatment for patent ductus arteriosus, a heart defect that is common in premature infants. The ductus arteriosus is a large artery that lets the blood bypass the baby's lungs before birth because the fetus gets oxygen through the placenta. If the ductus does not close properly soon after birth, the baby may develop heart failure. Treatment with indomethacin often closes the ductus, sparing many babies from the risks of surgery.

But babies with certain other life-threatening heart defects may require the opposite treatment. Drs. Rudolph and Heyman also discovered that the same drug can keep the ductus open, helping to restore some blood flow through the heart until the newborn is strong enough to survive lifesaving heart surgery. In the 1980s, a grantee at Yale University in New Haven, Connecticut, Charles Kleinman, MD, helped pioneer the use of echocardiography, a specialized form of ultrasound, to diagnose heart defects before birth. This test shows details of the heart's structure, blood flow and even the motions of its tiny valves. If the baby has a heart defect, doctors can plan for any special treatment the baby may need soon after delivery. The test also can show if the baby has an arrhythmia (a heart that beats too fast, too slowly or erratically), which can sometimes lead to heart failure and death. Drug treatment before birth often can correct the arrhythmia and save the baby.    

In spite of many advances in treatment, heart defects remain the leading cause of birth defect-related infant deaths. Today's March of Dimes grantees are pursuing a variety of approaches aimed at preventing heart defects and improving their treatment.  Many grantees are seeking to identify genes that contribute to heart defects, as a basis for developing novel treatments. Others aim to improve treatment of specific heart defects.

Faulty heart valves are among the most common heart defects. The heart has four valves that regulate blood flow through the heart's four chambers. The valves normally permit blood to flow forward, but prevent it from going backwards. "Heart valve defects can occur by themselves or occur along with other heart defects. Valve defects can have devastating consequences on the lives of pediatric and adult patients," said Kathryn Jane Grande-Allen, PhD, a grantee at Rice University in Houston, Texas, who is working to improve their treatment.

Serious valve abnormalities cause abnormal blood flow in the heart, sometimes causing the heart to work too hard, eventually resulting in heart damage. Currently available surgical options for valve repair or replacement in children are less than ideal. For example, replacement with a man-made valve requires life-long treatment with blood-thinning drugs, which can cause serious complications. Replacement with valves made from animal or human tissue often break down quickly in children, requiring additional operations.

Dr. Grande-Allen is studying the biological characteristics of normal and abnormal heart valve cells in young children. Very little is known about the specific characteristics of pediatric valve cells. This information is a crucial step toward achieving her goal of regenerating these cells to create replacement valves using a child's own tissue. "The quality of life for children with congenital valve disease would be revolutionized by the development of bioengineered pediatric heart valves," said Dr. Grande-Allen. This could eliminate the need for drug treatment and later re-operations, and allow the child to live a normal life.