tachycardia

Hearing her baby’s heartbeat for the first time can be one of the highlights of a woman’s pregnancy. In fact, checking the rate and rhythm of a baby’s heartbeat with a Doppler ultrasound is a routine part of each visit to the obstetrician during pregnancy. The fetal heart rate tells the doctor important information about the health of the baby.

A healthy baby’s heart usually beats 110-160 times a minute in the womb. It speeds up when the baby moves. Fetal heart rates also help count contractions and tell if a mother is going into labor too early. Signs of an abnormality with the fetal heart rate may require a referral to a fetal cardiologist to rule out structural problems with the heart, diagnose the rhythm and do something to manage it, if necessary.

Erik Michelfelder, MD, Director of Fetal Cardiology at Children’s Sibley Heart Center, says there are three categories of abnormality when it comes to fetal heart rate: Too fast, too slow and irregular.

Too fast

The most common reasons for a fetal heart rate that is too fast, known as tachycardia, are supraventricular tachycardia and atrial flutter. “With fast rhythms, we can give medications to the mom, which get to the baby through the placenta and convert the fetal heart rate back to normal,” Dr. Michelfelder said.

Too slow

Heart rates that are too slow, known as bradycardia, can be a sign of fetal distress. The most common reason for a slow heart rate is due to a condition called heart block, which is an interruption in the electrical connection between the top and bottom parts of the heart. In some cases, a surgical procedure to place a pacemaker may be necessary immediately after birth.

Irregular

An irregular fetal heart rate is often due to premature atrial beats. Irregular heartbeats usually resolve over time, while fast and slow heart rates typically require treatment.

The earliest that doctors can detect problems in fetal heart rate is 13 to 14 weeks into pregnancy, but Dr. Michelfelder said they commonly see them present at around 18 weeks. Arrythmias don’t typically present until later in pregnancy.

If any of these fetal heartbeat issues occur, the patient is most commonly referred to us to get a clear idea of what it is,” Dr. Michelfelder said. “We can rule out structural abnormalities and assess how well the heart is functioning in a baby who is having rhythm abnormalities. We can also make recommendations to a perinatologist (high risk obstetrician) to determine prenatal care.”

If a baby has a very low or very high fetal heart rate, a pediatric cardiologist will be asked to evaluate the child as soon as possible after birth. Depending on the issue, the case may require a transfer to a cardiac center like Egleston.

Lack of a normal heartbeat doesn’t always mean something is wrong with a baby. Reasons can also include the effect of medications or the baby’s position inside the womb. However, an abnormal heart rate can be a sign that the baby isn’t getting enough oxygen. Monitoring the fetal heart rate becomes a vital tool for doctors to be sure a baby is healthy and growing properly.

Learn more about the Sibley fetal cardiology program here.

For more information about Sibley Heart Center Cardiology and our pediatric cardiology specialists, click here.