I found this article on the American Heart Association’s website through a Google search for irregular fetal heart beats. The entire article is very interesting, but I especially found the part at the very end about “bradycardia” to be encouraging. Thank you for your comments, emails, phone calls and prayers. We continue to “prepare for the worst and hope for the best,” as Bob has said tonight.
Ask the Pediatric Cardiologist: Irregular Heart Rhythm
Question: My obstetrician detected an irregular heart rhythm during a regular visit today. I am 24 weeks pregnant and everything else has been fine. What is an irregular heartbeat and what does it mean for my unborn baby? Will this problem go away before my baby is born? Do I need to take medication?
Answer: An irregular heart rhythm is usually benign, but your obstetrician may refer you to a pediatric cardiologist for a fetal echocardiogram to better define the heart rhythm.
The normal fetal heart rate is between 120 and 160 beats per minute. The heartbeat is usually regular with only a little variation in the heart rate. Each heartbeat comes from the top part of the heart (atrium) beating first, followed immediately by the bottom part of the heart (ventricle). The bottom part of the heart is what causes blood to leave the heart and make a sound on the heart monitor.
The most common cause of an irregular heart rhythm is when the top part of the heart beats too early (premature atrial contraction, or PAC). Sometimes this premature beat is transmitted to the bottom part of the heart; other times the communication between the top and bottom part of the heart is interrupted after a premature beat.
An early beat that is transmitted or blocked will cause an irregularity in the heart’s rhythm. These premature atrial contractions are very common in the second half of pregnancy and usually don’t cause any problems. They may persist after the baby is born, but usually go away by one month of life. Medication isn’t necessary.
These premature beats can cause problems in a small percentage of cases if multiple consecutive premature beats occur. When this happens for a long enough period, it’s called tachycardia (fast heart rate). If the heart rate stays above 200 beats per minute for a long period of time (hours or days), it could damage the baby’s heart and other organs. If tachycardia occurs, your pediatric cardiologist and obstetrician will recommend medicine for you to take to help regulate your fetus’s heart rhythm. If there are any signs of damage to the fetal heart, it may be recommended that you be hospitalized while beginning the medicine. If you are put on medicine, it is likely the baby will need to take the same medicine after birth.
Most fetuses with tachycardia have a good prognosis if the heart is structurally normal. Some fetuses have a pattern of frequent blocked premature contractions resulting in a low heart rate (bradycardia). This does not usually cause any problems to the baby as long as the heart rate remains above 60–70. Some fetuses with premature atrial contractions can have bradycardia on one visit and develop tachycardia later on. An irregular heart rhythm is not usually worrisome in the fetus, but should be followed closely by your obstetrician.