Understanding Congenital Heart Disease and its Diagnosis During Mother’s Pregnancy
Congenital heart defects are abnormalities of the anatomy of the heart. They are called congenital because they occur when the heart is forming in the womb and babies are born with them — hence they are a type of birth defect. Occasionally they are hereditary due to alterations in genes and their transmission in offspring. However, the majority of congenital heart defects are not inherited, but rather, they are created by errors in cellular development during gestation. These errors can be caused by environmental factors (toxins, drugs, alcohol, smoking) but most commonly are created by simple “mistakes during the embryological formation of the heart in the fetus. There are also some maternal health conditions that can increase the risk of congenital heart disease in the infant.
With technological advances, it is possible to diagnose heart disease very early in pregnancy. Currently, the diagnosis can be made between weeks 14–16 (4 months of pregnancy), although the cardiac anatomy is better visualized at week 20. The performance of an expert fetal echocardiogram can diagnose a multitude of congenital heart defects. While some serious cardiac disorders may go unnoticed because the fetus’s heart works differently from the heart in a newborn, fetal echocardiography is becoming increasingly accurate. It is sometimes even very difficult to see the heart due to the fetal position or because of obstruction caused by the mother’s own tissue (such as if the mother is obese), given that the diagnosis must be made through the mother’s womb.
When the baby is born, there are circulatory changes, the lung begins to work, fill with air, and as the pressures in the lungs begin to change, the lung opens and fills with air. Blood begins to flow through the lungs (which is not the case in the fetus) and circulation becomes typical for the newborn infant.
If heart defects are not diagnosed prenatally, congenital heart defects that prevent normal infant circulation may become apparent as the fetal structures close and pressure changes occur in the lungs and various blood vessels.
When congenital heart disease is diagnosed in pregnancy, it is possible to prepare the mother, as well as the medical team. Plans can be made, including where the baby should be delivered (such as at a hospital to take care of critical heart disease in the newborn) and the parents have time to prepare themselves emotionally for all that might need to be done for their baby. There are a wide variety of congenital heart defects, and some of these “defects” may be normal features of the fetal (developing) heart and only become abnormal when the baby changes from fetal to infant circulation. Some parents may be informed that their baby may have a mild or inconsequential heart “defect” that may never need treatment, and that may regress or disappear on its own. Other parents may benefit from learning that their child will be born with a defect that will likely require more urgent treatment after birth, including the potential for surgery or interventional catheterization. In these cases, it can be extremely helpful for the family to meet with the surgeon or interventional cardiologist prior to the delivery of their child, as this gives them an opportunity to ask questions and to become more prepared.
When heart disease is diagnosed in the newborn, the symptoms can vary from mild to fast breathing (which can impair the ability of the infant to feed — so they “fail to thrive”) to cyanosis (blue coloration) or heart failure. Cyanosis occurs if heart disease causes a mixture of non-oxygenated (venous) blood with the body’s oxygenated (arterial) blood, or by an obstruction to the flow of blood to the lungs, which can interfere with the ability of the baby to oxygenate the blood. Cyanosis occurs when unoxygenated blood is pumped to the body. In this case, the blood, which should go to the lungs, goes to the systemic side, without adequate oxygenation of the tissues. Heart failure in children manifests as tiredness and/or sweating during intake (feedings), increased respiratory rate, and/or delayed weight gain.
In the event of any indication of congenital heart disease, an expert — a pediatric cardiologist — should be contacted who will explain all the important points: anatomy of the heart disease, repercussions, medical and surgical treatment options from an integrated multidisciplinary team, plus likely tests and procedures that may be needed in the post-birth period…
Parents generally comment that it is extremely helpful to receive a diagnosis prior to the birth of their baby. It provides them with an opportunity to become educated and to begin to make important decisions, such as where they may wish to receive treatment. It also helps them prepare emotionally for childbirth that is not what they expected. The ability to provide accurate and timely prenatal diagnosis has been a major advancement in the field of treating heart defects in children. Fortunately, with the efforts of health professionals like Dr. Ross Michael Ungerleider, there have been key developments in the diagnostic process.
Dr. Ungerleider is notably known as a surgical leader, innovator and mentor, author, and coach who benchmarked the incorporation of echocardiography in the Operating Room (OR), which is now an international standard of care practiced in children’s hospitals around the world. He has had experience in the profession of surgery for heart defects in children for close to 40 years and recalls the era prior to the advent of fetal echocardiography when babies with congenital heart disease were not diagnosed until after they were born.
“Sometimes, these babies got pretty sick and often after they were sent home because no one knew they had a heart defect,” says Ungerleider. “There are some heart defects that don’t present until several days after a baby is born due to the transitioning from fetal to infant circulation, and these babies would present more emergently to the hospital — often creating understandable distress for the family and we would be forced to try and treat babies who were in very serious and deteriorating condition. As prenatal diagnosis has gotten better, along with our ability to ensure providing more precise surgical repairs (using echocardiography in the operating room), outcomes for these babies keep getting better and better.”
