Having a baby with a health problem is hard. Knowing what you are facing a head of time (or at least very soon after delivery) is helpful emotionally and, for some babies, it can be lifesaving. For example, every pregnancy in North America is screened for neural tube defects (NTD) a condition where the spinal cord and sometimes even the brain fails to form correctly. For some affected children a NTD is sadly fatal; however, for some children knowing about a NTD in advance can help improve outcomes. Some babies can have fetal surgery during pregnancy to correct the defect before birth improving their outcomes. For others, knowing about a NTD means planning for the delivery at a center with a pediatric neurosurgeon and most often a c-section, as these two things improve outcomes. Testing for neural tube defects in not cheap – it involves blood tests and an ultrasound at 16-20 weeks in the pregnancy. The medical community has deemed screening for NTD important and most patients agree and desire the testing.
All babies in the United States are also screened for congenital hypothyroidism (under activity of the thyroid gland). The incidence is 1/4,000 births. Congenital hypothyroidism is a very serious condition. Without enough thyroid hormone the developing brain is damaged permanently leading to mental retardation (this is called cretinism). The test is an inexpensive blood test. If it is abnormal more testing is needed. The treatment to prevent cretinism is a pill that costs about 1 cent a day. Clearly screening and treating for congenital hypothyroidism is important - a devastating condition that can be prevented by a pill.
So what about congenital heart defects? These defects affect 9/1,000 births, so they are more common than NTD and congenital hypothyroidism. Now many heart defects are not serious, meaning surgery or intervention in the first year of life is not needed. For example, atrial septal defects (a hole between the two atria, the top chambers) are watched for at least 2 years before they are closed. Knowing about these defects at birth is less important. However, 2 out of every 1,000 newborns (that is 25% of babies with a congenital heart defect) will have a critical defect, meaning knowing about this at birth (or before birth if possible) is important. Less than 10% of congenital heart defects are diagnosed before birth? Why?
An ultrasound at 16-20 weeks (the same scan used to to screen for NTD) is capable of picking up 90% of congenital heart defects if (and this is important) the ultrasonographer is appropriately trained and gets a good look at all 4-chambers of the heart. This is harder than it sounds. The baby must be back down and still. Trying to get a good view of a heart that is 2 cm or less in size, that is beating 160 times a minute, in a baby who is moving, though a mother’s belly can be a challenge to say the least. If any potential concerns are raised or other abnormalities identified on ultrasound then the baby should have a fetal echocardiogram, a much more detailed assessment performed by a specifically trained technician and interpreted by a cardiologist.
If a 4-chamber view of the heart should pick up 90% of defects but isn’t then the question is really should different screening be recommended? Is this even important?
Well, I have a son with congenital hypothyroidism and one with a critical heart defect. I do not believe one defect is more or less important than the other. If screening for NTD and hypothyroidism is important (and it is!) why is screening for critical congenital cardiac defects not as important? Are the 2 out of every 1,000 babies born with a critical cardiac defect not as important as the 1 out of 4,000 with hypothyroidism and the 1 out of 1,000 with a neural tube defect?
I don’t have the answer as to the best screening tool. I had my ultrasounds in my pregnancy performed by some of the best perinatologists and ultrsonographers in the world. All were trained by Dr. John Hobbins, a master and really the father of obstetrical ultrasound. Because I took a medication during my pregnancy that can cause cardiac defects I had not one but two fetal echocardiograms. Both failed to detect Oliver’s critical pulmonary stenosis that needed surgery when he weighed 1,200 g (he also had an atrial septal defect, but that was watched for two years, so not part of his critical defect, but important to note that both his critical and non critical defects were missed).
My point? If some of the best doctors and ultrasonographers in the country can’t pick up a defect after a level II ultrasound with a 4-chamber view and two fetal echocardiograms then a different test may be needed. In addition, some critical defects (like abnormal coronary arteries) cannot be identiifed on ultrasound or echo at all.
As with everything in medicine, more studies are needed/underway. However, in the mean time pulse oximetry (a painless evaluation of the blood oxygen level) performed after 24 hours of age can pick up 50% of critical cardiac defects in newborns, it requires no specialized training, is in every hospital in the Western world, and costs maybe one or two dollars. At the most.
Isn’t that a good place to start?
Here are my two sweethearts. Critical heart defect on the left and hypothyroidism on the right. Equally important and equally potentially devastating.