Heart rate drops may occur in newborn babies while they are cared for in the hospital and always cause a lot of anxiety for parents. Last month, I spent an hour explaining this problem to parents who, after reading multiple articles on the internet, became extremely worried and confused about this subject.
The good news about most cases of heart rate drops in newborn babies is that this condition is usually not life-threatening and resolves on its own over time. The bad news is that it can persist for some time, and everybody gets frustrated, especially if the baby is doing well otherwise and could be potentially discharged home if not for the heart rate drops.
This article will explain what heart rate drops are, how they are called in medical jargon, their frequent causes, and symptoms or problems that may accompany this finding.
The article aims to provide information for parents of babies affected by heart rate drops so they can have more fruitful discussions about this subject with their baby’s doctors.
Background information on heart rate drops (definition and explanation of vital signs)
Vital signs abnormalities in newborn babies
When a baby has any problem (prematurity, feeding issues, low glucose, or breathing problems), such a baby would be placed in a NICU or observation nursery. Once this occurs, we will closely follow various parameters for each baby. Some of those parameters are called vital signs. Body temperature, respiratory rate, heart rate, and blood pressure are all part of vital signs.
To help us follow and observe babies continuously, most newborns with health issues will be placed on cardiorespiratory monitors.
Cardiorespiratory monitors provide information on the baby’s respiratory rate, heart rate, blood pressure, and oxygenation levels (so-called oxygen saturation). Most monitors record all those parameters for at least 24 hrs allowing us to look back and analyze any events that occurred in the past. Specific abnormalities found while observing a baby or due to alarms going off on the monitors may be cause for concern, especially when correlated with the baby’s clinical condition.
To learn which findings may concern clinicians, let’s talk about some definitions used to describe vital signs abnormalities. Even though the topic of my article is heart rate dips in newborn babies, please familiarize yourself with all the terms described below because many times, different vital signs abnormalities are associated with each other; and that association may help us with the diagnostic process.
Hypothermia is a term used to describe abnormally low temperature. Hypothermia is common among premature babies, sometimes occurs in full-term babies due to low environmental temperature, and occasionally is a sign of trouble (infections).
Hyperthermia is a term used to describe fever or abnormally high temperature. Fever may occur in babies due to high environmental temperature (for example, baby in an incubator with the temperature set too high), or it may be due to developing infection or sepsis.
A baby’s average body temperature should be around the same as in an adult: 36.6 degrees of Celsius.
The average respiratory rate in an awake baby fluctuates between 40-60 breaths per minute. When a baby is breathing faster than 60 per minute, we say that baby is tachypneic. When a baby is breathing less frequently than 30-40 minute, we will say that baby is hypoventilating. Finally, if the baby stops breathing entirely for longer than 20 seconds, we cal it apnea or apneic event (see my article on apnea of prematurity here).
Frequent and prolonged apneic episodes often lead to heart rate drops and decreased levels of oxygen (desaturations or hypoxia).
The average heart rate in awake newborn babies fluctuates between 120 – 160 per minute. However, sometimes deeply asleep babies may have heart rates down to the 80s or 90s. Heart rates at those levels in awake babies or below that level in a sleeping baby would be called bradycardia. Sudden heart rate drops by 20 per minute in feeding, or sleeping baby would also be called periodic bradycardia.
Hypoxia is a general term to describe low oxygen levels in our body. It is challenging to measure oxygen levels directly without a blood test. Therefore we use oxygen saturation monitors to do that. Oxygen saturation monitor assesses the percentage of blood hemoglobin attached to oxygen, which may give us a general idea about oxygen levels in our body. That’s why instead of talking about oxygen levels, nurses and doctors often use the term: oxygen saturation or in short saturation.
Good oxygen saturation in a baby observed in the nursery should be above 92% and ideally in the high 90s. There are some situations in babies, particularly if the baby is premature or has a congenital heart condition, that we would tolerate lower oxygen saturation and not treat it. However, in general, any oxygen saturation lower than 92% in a newborn baby would prompt us to investigate the causes and consider treatments.
Diagnostic approach to heart rate drops in a baby
Any baby with significant heart rate drops should be placed on a cardiorespiratory monitor to assess the severity of episodes and their correlation with respiratory rate and oxygenation levels.
In addition, if we want to consider other causes of heart rate dips than “just” prematurity, immature feeding pattern, or “physiologic” reflux, we may need to run some additional tests described below.
We perform blood cultures and CBC (blood counts) if we suspect an infection.
For abnormalities in the central nervous system, we can order EEG (electrical study of the brain) and imaging studies of the brain such as ultrasound, CT, or MRI.
Suppose the baby is suspected of having an abnormality in the heart. In that case, we can do ECG (electric study of the heart function) and Echo (ultrasound study of the heart to look at anatomy and function of the heart).
For babies with severe choking episodes, while feeding not explained by their immaturity, we may need to rule out anatomic abnormalities in their respiratory and digestive systems. For example, abnormal anatomy (structure) of the throat, stomach, esophagus, trachea, or lungs may contribute to such severe episodes. When we suspect that, doing CTs or X-rays with or without contrast would make a lot of sense.
I want to emphasize that most newborn babies with heart rate drops do not need any additional tests beyond just careful clinical observation. However, all these babies need to be monitored frequently or continuously, so we do not miss clues about potential etiologies that would require additional testing and our attention.
The most important cause of heart rate drops or apneic episodes that I always want to rule out is infection or sepsis. It is essential because it may be life-threatening if not recognized quickly and not treated right away. Typically, babies with an infection will present with sudden deterioration and abnormal vital signs. In addition, if not treated, babies with the infectious disease will worsen with time, in contrast, to well-appearing babies with heart rate drops due to their immaturity or reflux.
Heart rate drops only during feedings versus heart rate dips during sleep and feedings versus baseline slow heart rate.
In general, one can say that if heart rate drops are associated mainly with feedings and do not occur at sleep or rest, they are probably due to immature feeding abilities, significant reflux, and occasionally due to anatomic abnormalities. Also, sometimes sick babies with respiratory or heart conditions get tired quickly with feedings, leading to heart rate drops during bottle or breastfeeding.
When heart rate drops occur mainly at rest or while asleep, their causes are different:
- infections or sepsis
- apnea of prematurity
- heart arrhythmias or low baseline heart rate
- conditions of the central nervous system, including seizures
- metabolic abnormalities
- reflux or spitting (gastroesophageal reflux)
Some conditions associated with heart rate dropping during feedings.
Uncoordinated feeding process
Uncoordinated feeding or immature feeding is probably the number one cause of heart rate drops during the feeding.
The feeding process consists of three unique steps: sucking, swallowing, and breathing. These three skills have to be coordinated, so the baby does not get tired too quickly and does not aspirate milk into the lungs.
Each baby with feeding issues may face unique challenges. For some, it is too difficult to suck effectively. Others are unable to coordinate suck and swallow reflexes. Some “forget” to breathe during feeding and continue sucking until they run out of breath and their heart rate drops, and oxygen levels decrease. Finally, some babies have hard time coordinating swallowing with breathing, so food does not get into their lungs. As a result, they develop frequent microaspirations, causing their heart rate to drop or oxygen levels to decrease.
Immature feeding skills occur primarily in premature babies but still can affect babies born after 37 weeks or babies with other medical conditions that make them sicker or tired.
Usually, immature feeding skills get better with time and proper training. By training, I mean consistently using proper feeding techniques and not forcing baby to eat by mouth if the baby is tired or not ready physiologically to do it yet. The prognosis for resolution of feeding difficulties due to immaturity is excellent, and in almost all cases, babies will be able to eat by mouth without any problems (scientific article).
Severe gastroesophageal reflux
After we swallow food, it travels from our mouth to the esophagus and then into the stomach. Under normal conditions in adults, food is prevented from returning from the stomach into the esophagus unless we vomit. The “guardian” is a circular muscle called the lower esophageal sphincter that constricts after food passes into the stomach and does not allow for its return.
This lower esophageal sphincter is underdeveloped or not fully functional in all newborn babies. Therefore, most full-term babies and probably all premature babies have some degree of reflux. Non-clinicians and parents will tell you that their baby has spit-ups or is a spitter.
If the baby can feed well, is growing and gaining weight well, and reflux does not interfere with their breathing, we do not worry about its existence. We know that with time, spit-ups get better, and usually, by 6-9 months of age, all babies will outgrow this phase.
If reflux causes severe heart rate drops during feedings, and while asleep, we may need to diagnose it and treat it. There are many controversies regarding the diagnostic process and whether and how to treat reflux, so I will leave it for another article. I will only say here that reflux is not to be treated with any medications or surgeries in most cases. Its management will usually be limited to proper feeding technique, thickening milk, and proper positioning after feedings (scientific article).
Anatomic abnormalities of respiratory or digestive systems
Certain anatomic abnormalities may contribute to heart rate drops during feedings. An example of such problems could be a mass that is narrowing “feeding or respiratory passages” or abnormal connections between respiratory and digestive track leading to aspirations (fistulas). The latter is called a tracheoesophageal fistula. Usually, babies with these conditions are easy to spot as they develop severe symptoms during and after feedings. Often, they will have choking-like episodes, cough, salivating, significant apneas, heart rate drops, and long oxygen desaturations.
In addition, some may develop chronic tachypnea and need oxygen therapy due to aspiration pneumonia.
Conditions affecting the function of respiratory and cardiovascular (heart) systems
Newborn babies with conditions affecting the heart and lungs may have tachypnea (fast breathing) as a baseline. Therefore it will be difficult for them to coordinate suck and swallow reflexes with breathing leading to heart rate drops and even aspiration during feedings. Generally, we avoid feeding babies who present with such a fast breathing rate or have labored breathing.
For babies who have a congenital heart condition, another symptom that may be prominent during feedings apart from heart rate drops or faster breathing will be increased sweating.
Diagnosis and treatment of those conditions will depend on a suspected specific disease of the lungs or heart.
Conditions causing heart rate drops mainly during sleep or both sleep and feedings.
Apnea of prematurity
Apnea of prematurity may cause heart rate drops during sleep. Apnea is defined as cessation of breathing for 20 seconds or more and of lesser duration if accompanied by significant heart rate or oxygen changes.
Apnea will be called “apnea of prematurity” if the most likely cause of apnea is immaturity due to premature birth.
Apnea of prematurity will not cause heart rate drops during feedings. However, it may coexist in the same baby that is affected by heart rate drops while being fed. Furthermore, the same global immaturity leading to apnea of prematurity can cause immature feeding skills resulting in heart rate drops.
I wrote a detailed article about apnea of prematurity covering diagnosis, differential diagnoses, treatment, and prognosis, if your baby was born prematurely, read it!.
Conditions of the central nervous system that can affect heart rate and its variability include:
- seizure disorders
- severe hypoxia at birth causing brain damage (usually associated with very low Apgar scores at birth)
- hydrocephalus (enlargement of structures holding fluid in the brain)
- masses in the brain
- developmental abnormalities of the brain
- hemorrhages in the brain
Usually, babies affected by abnormalities in the central nervous system will have a history or symptoms, allowing us to suspect such an etiology. For example, babies who had low Apgar scores at birth, abnormal ultrasounds during pregnancy, low muscle tone, or seizures will be suspected of having those conditions and will need further work.
Metabolic abnormalities (glucose, acid, calcium, and others)
Abnormal potassium, calcium, sodium, glucose, or acid levels in our body may influence muscle tone, cause seizures, or affect the quality of our breathing and heart rates directly or indirectly.
Heart rate drops in metabolic conditions are not their most common presentation; however, it is easy to diagnose them if needed, just with a simple blood test.
Infections or sepsis
Whenever a newborn has a sudden change in vital signs or its condition, we need to consider infections as a number one diagnosis that must be either confirmed or ruled out. It is that way because infections are hazardous; they can kill you. But, on the other hand, infections are treatable if recognized early, and often a course of antibiotics can cure patients without any long-term consequences.
New onset of apneic episodes, heart rate drops, desaturations, or abnormal body temperature should prompt us to consider infections as a possible diagnosis. In most cases with such a history, we would do some blood tests (blood cultures and CBC) and start a course of broad-spectrum antibiotics until the infection is confirmed or ruled out.
Arrhythmias – heart rhythm abnormalities
Arrhythmia is a term used to describe irregular heart rhythm or abnormally low or high heart rate. Arrhythmias may occur due to intrinsic heart problems or external factors such as brain damage or metabolic abnormalities. Arrhythmias may cause heart rate drops both during feedings and while asleep. With arrhythmias, irregular heartbeats will be occurring very frequently and will not be difficult to detect if we place the baby on the bedside heart rate monitor.
When an arrhythmia is suspected, the first steps in diagnosis involve performing an electric study of the heart (ECG) and sometimes ultrasound of the heart (Echo) to make sure that the anatomical structure of the heart is fine.
Treatment of arrhythmia will depend on its severity. It may involve only observation, medications, and occasionally laser surgery.
Treatment and prognosis – time and patience are the best solutions
Treatment of heart rate drops will depend on their etiology (cause). For example, if the problem is due to immature feeding skills, patience and allowing the baby time to learn how to eat effectively is the best solution.
If the issue is due to GE reflux, proper feeding technique, sometimes thickening the milk, and time are the best solution. Occasionally, GE reflux is treated with medications and very rarely with surgery.
Apnea of prematurity resolves with time; nonetheless, sometimes we treat it with Caffeine and occasionally with some type of respiratory support.
Infections we treat with antibiotics.
Anatomic abnormalities may require surgical fixing; luckily, those conditions are rare.
Conditions such as metabolic abnormalities, cardiac or respiratory issues, or central nervous system diseases may need specialized diagnostic techniques and treatments of which explanation is beyond this article’s scope. However, keep in mind that latter diseases are infrequent causes of heart rate drops in newborn babies, especially if those babies otherwise are well appearing and do not have additional medical problems.
In general, I want to state that most cases in which babies have heart rate drops during feedings or while sleeping have an excellent prognosis and resolve with time. So, for most situations, allowing time for resolution and being patient is the best remedy.
My final advice to parents of babies with heart rate drops: Please do not focus on watching the monitor and be anxious about every blip or alarm. Monitors produce a lot of artifactual (fake) warnings. Instead, try to learn your baby. For example, observe your baby during sleep and feedings. Learn how to notice that baby stopped breathing, its color changed, and its tone decreased. Learn how to recognize that baby needs a break during feedings, to remove the bottle from its mouth so baby can recover its regular breathing.
Finally, I encourage you to sign up for a CPR (cardio-pulmonary resuscitation) course on the American Heart Association’s website. It is always a great idea to learn how to help infants and adults who suddenly developed choking episodes or went into cardiac arrest. All adults and teenagers should learn those life-saving skills. We never know when they can come in handy.
This article is only for general information purposes. It should not be viewed as any medical advice. There is always a chance that information here may be inaccurate. It would be best if you always discussed all health-related matters with your doctor before making any decisions that may affect yours or your family members’ health.