Bradycardia and Apnea in Premature Babies

In premature babies, apnea and bradycardia often occur together, along with low blood oxygen levels. Apnea is a period when breathing stops, while bradycardia is a slow heartbeat.

First, apnea occurs and the baby will stop breathing. Because the baby isn’t breathing, blood oxygen levels will fall. The heart slows down in response to the low blood oxygen levels.

Together, apnea and bradycardia are often called “As and Bs” or "spells" and a low blood oxygen level is often called a desaturation or “desat.”

Bradycardia and Apnea in Preemies
Verywell / Sisi Yu

Oxygen Saturation

Oxygen saturation measures the amount of oxygen-carrying hemoglobin in the blood. The blood of a term baby, like that of a child or adult, should be 95% to 100% saturated with oxygen.

The blood of a premature baby receiving extra oxygen is usually maintained between about 88% and 94% saturation, not higher, to prevent retinopathy of prematurity, a serious eye condition.

In the hospital, pulse oximetry is used to measure the amount of oxygen in the blood. When the blood does not have enough oxygen, it is called a desaturation. Desaturations can cause a bluish tint to the lips or skin and cause a baby to lose tone or become “floppy.”


Apnea means a period in which breathing stops. In premature babies, apnea is any pause in breathing that lasts longer than 20 seconds, causing bradycardia, or a drop in the baby’s blood oxygen level. 

Premature babies have immature nervous systems and are prone to having episodes of apnea. Sometimes, apnea will cause the baby’s heart to beat too slowly, called bradycardia.

In the NICU, premature babies are hooked up to monitors that sound alarms when their breathing has these long pauses. Usually, a gentle pat on the back is all that’s needed to remind the baby to breathe again, but sometimes babies need help breathing or extra oxygen when they’re apneic.

Most premature babies outgrow their apnea by the time they’re ready to go home, but some babies will still have occasional spells of mild apnea. If that happens, parents will take their baby home with an apnea monitor, which will go off if the baby stops breathing.


Bradycardia means a slower than normal heart rhythm. In newborns, a heart rate is termed bradycardia if it falls below 100 beats per minute in a baby less than 1250 g (2 lbs. 12 oz.) or to less than 80 beats per minute in a bigger baby. 

When babies are in the NICU, their hearts are monitored, and episodes of bradycardia are treated with stimulation. If bradycardia continues, medications such as caffeine may be used to treat the condition.


Apnea and bradycardia have many causes in premature babies. Infection, anemia, and problems in the brain can all cause As and Bs. The most common cause of apnea and bradycardia among premature babies in the NICU, though, is a condition called apnea of prematurity.

Apnea of prematurity is a condition caused by immature nervous and muscular systems. Apnea of prematurity occurs most frequently in younger premature babies; as gestational age decreases, apnea of prematurity increases.

Only 7% of babies born at 34 to 35 weeks gestation have apnea of prematurity, but over half of babies born at 30 to 31 weeks have the condition.

Apnea can occur because the process in the brain that tells the baby to breathe fails, and the baby stops breathing entirely (central apnea) or because the baby’s immature muscular system isn't strong enough to keep the airway open and airflow is blocked (obstructive apnea). Mixed central and obstructive apnea also occurs.

Long-Term Effects

Doctors aren’t sure what the long-term effects of apnea and bradycardia are. They know that bradycardia causes a temporary reduction in the brain’s blood and oxygen levels.

They also know premature infants who had more days with recorded episodes of apnea have lower scores at age 3 on tests that measure developmental and neurological outcomes, but they can’t say for sure that apnea and bradycardia cause the lower scores.

One thing that doctors do know is that apnea and bradycardia do not cause sudden infant death syndrome (SIDS).

Although premature babies, in general, have a higher SIDS risk than full-term infants, apnea of prematurity does not cause higher SIDS rates.


When babies in the NICU have an episode of apnea or bradycardia, the monitors that record their heart rate and breathing start to alarm. Sometimes, just the sound of the alarm is enough to stimulate the baby to breathe again, and the baby is breathing well before the nurse even has time to respond.

Other times, the alarm isn’t enough. Stimulation, through rubbing or patting the baby, will be used. If the baby still does not recover, then the baby will be given breaths with a bag and mask.

Babies who have frequent bouts of apnea may be placed on continuous positive airway pressure (CPAP) to help them breathe or may be mechanically ventilated. Medication can also be used to treat apnea of prematurity.

Caffeine is a relatively new treatment for apnea that has few side effects and has been largely successful.

Preventing Further Spells

Knowing what triggers episodes of apnea and bradycardia can help nurses and parents minimize the number of spells that premature babies have. Apnea and bradycardia tend to occur during transitions out of deep sleep, so it is important to allow babies to have long periods of deep sleep.

Coordinate your visits to the NICU with feeding and assessment times, and use quiet voices if you are visiting when your baby is sleeping. Fluctuations in incubator temperatures can also cause As and Bs, so try to maintain a stable temperature in the incubator by keeping incubator doors closed as much as possible.

Nipple feeding is another common cause of apnea and bradycardia. When feeding a premature baby at the breast or bottle, the pacing is critical, especially at the beginning of a feeding.

If your baby seems to be sucking continuously without pausing to breathe, pace the feeding by periodically pulling the nipple out of his or her mouth.

When Will It Go Away?

In most babies, apnea will begin to resolve around the time that they were due to be born, and around the time that they begin eating well enough on their own to gain weight consistently and maintaining a warm temperature outside of an incubator.

Some babies, though, will continue to have episodes of apnea and bradycardia even after they are ready to leave the NICU in every other way.

Most hospitals require babies to have a certain number of days without apnea or bradycardia before they can be discharged to make sure that they have outgrown apnea of prematurity completely.

Babies who still have episodes of apnea or bradycardia even after they are ready to go home in every other way may be discharged from the hospital with a home apnea monitor.

These monitors are controversial because they don’t have clearly demonstrated medical benefits and are hard for parents to live with, but are still widely used for babies with persistent apnea.

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6 Sources
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