What is respiratory distress in newborns?
In newborns, ‘respiratory distress’ describes signs of breathing difficulties such as rapid, shallow breathing, flaring of the nostrils, blue-tinged lips or blue finger digits, coughing, grunting, and chest retractions.1 Rapid breathing in newborns is classed as above 60 breaths per minute, at which the infant enters the condition of tachypnoea.2 Research indicates that incidences of respiratory distress in newborns are on the rise.3,4
This information may be distressing to new or expectant parents, however, it is important to recognise the role risk factors play in this increased incidence. Understanding which risk factors are affecting each child allows for preventive action to be taken to either mitigate the risk or better prepare for the outcome.
As such, this article aims to explore several different risk factors for respiratory distress in newborns.
Risk factors
Risk factors for a disorder are proven to increase the likelihood of the outcome occurring, however, the magnitude depends on the strength of the association.5
In this article, the following risk factors for respiratory distress in newborns will be discussed:
- Birth asphyxia
- Premature delivery
- Caesarean section
- Male sex
Birth asphyxia
Birth asphyxia is one of the leading causes of respiratory distress in newborns.6 Perinatal or birth asphyxia occurs when there is a lack of blood flow to or from the foetus or newborn, during their birth.7 As the foetus receives oxygen via blood flow through the umbilical cord, from the placenta, a disruption to this process can result in tissue damage as a result of a lack of oxygen to the vital organs, which can result in multi-organ failure or death if not amended soon enough.8
The Apgar score ascribed to the newborn is one of the diagnosis criteria for birth asphyxia and it is a test routinely undertaken following the birth of a baby. It assesses multiple factors to provide a holistic measure of the baby’s physical condition.
A score of ≥7 shows that the newborn is in good health.9 This test is conducted in the first 5 minutes following birth and a score of between 1-6 at one minute and less than 4 at 5 minutes indicates birth asphyxia.6 However, the Apgar score is not a perfect metric as it can be influenced by factors such as premature birth and maternal sedation.10
Alternatively, the pH or lactate of the umbilical cord can be measured as this has shown to be a key predictor in diagnosing birth asphyxia.11 A low pH in the artery of the umbilical cord indicates metabolic acidosis, which occurs when less oxygen is being exchanged with CO2, meaning the proportion of CO2 is higher than it should be.12 This results in the blood becoming more acidic due to the increased presence of H+ ions, which are by-products of CO2 reacting with water in the bloodstream, this causes the pH to drop.13 Furthermore, when there is a lack of oxygen present during respiration, umbilical lactate production increases, therefore an increase in the rate of this reaction can also be used as a predictor of asphyxia.14
While the circumstances leading to birth asphyxia may be hard to avoid, this information underlines the importance of accurate and consistent monitoring of foetal and neonatal respiratory rates, so that if any potential identifiers of asphyxia occur, they can be quickly addressed.
Premature delivery
Premature delivery or preterm births are any births that occur before the full term of 37 weeks, however, births before 32 weeks account for the majority of deaths and disorders for this group.15 As noted in the previous section, premature delivery can interfere with the accuracy of APGAR scores following birth. Premature delivery itself is therefore a risk factor for birth asphyxia.16
While it may lead to an increased likelihood of asphyxia, premature delivery is also an independent risk factor for respiratory distress itself.17 For very premature births (before 32 weeks), chronic respiratory complications are the most common adverse outcome.18 The lung function of preterm babies improves as they get older, but they are at their most vulnerable in the early weeks of life, which explains the need for active monitoring of their respiratory health.19
The impaired respiratory function of babies born prematurely can manifest itself in a combination of ways.20 One of the most prominent conditions is a deficiency of pulmonary surfactant.21 Pulmonary surfactant consists of a mixture of phospholipids which line the inside of the alveoli within the lungs - the site of gas exchange.22 The presence of the surfactant within the alveoli is imperative for maintaining the structure’s stability by reducing surface tension; without it, gas exchange is compromised.23 This is a recurrent issue in preterm deliveries as the majority of surfactant produced in gestation occurs during the 30-32 week period, therefore babies born before 32 weeks are often born with a surfactant deficiency.24 However, for premature deliveries, surfactant therapies do exist, including non-invasive options that do not require intubation.25
Caesarean section
While the risks associated with deliveries before 32 weeks are clear, there also remain risks associated with delivery between 34 and 37 weeks - namely in the performance of a caesarean section.26 Furthermore, caesarean section at term (37-40 weeks) has also been shown to be a risk factor for severe respiratory distress.27
Caesarean section is often performed in favour of vaginal delivery in circumstances where either the baby and/or mother’s health is at risk such as preeclampsia or breech birth.28 Preeclampsia is a condition that develops during pregnancy when disruption of blood flow from the placenta results in an increase in blood pressure (hypertension) and increased protein in the urine (proteinuria); it can affect both the mother and child with potentially fatal consequences if it advances to eclampsia.29 Hence caesarean section is often opted for in such circumstances to expedite the delivery and better ensure the safety of mother and child.28 However, whilst the decision to undertake a caesarean section may be out of the mother’s control in circumstances such as this, this choice of delivery is also shown to increase the risk of respiratory distress when done so electively.27
Male sex
One factor that is completely uncontrollable in pregnancy is the sex of the baby. Therefore, it may come as a surprise to learn that this can also impact the adverse risk of the event of respiratory distress.
It has been shown that male infants are more likely to suffer from respiratory distress-syndrome-related mortality and that their neonatal mortality rates are higher than their female counterparts.30 On top of this, caucasian male babies have an increased risk compared to non-white male babies, however, this association has not been proven in term or late-term infants.31 But in term and late-term babies, caucasian babies have been proven to be an independent risk factor for respiratory distress, regardless of the sex.
Summary
Respiratory distress is a common affliction that affects many children around the world. The disease is characterised by affected chest retractions, a respiratory rate above 60 breaths per minute and physical signs such as a blue colouring of the infant, a flaring of their nostrils and grunting.
Research indicates that cases of respiratory distress in newborns are on the rise, along with the severity of their complications. The good news is however that increased scientific effort has gone into determining the risk factors for the condition so that it can be better prevented or managed.
One such risk factor is birth asphyxia, which occurs when blood flow from the placenta to the foetus, during, before or after birth is compromised, leading to the baby receiving less oxygen than it should. The severe complications of incidence of this include hypoxia, hypocapnia and metabolic acidosis, all of which can lead to tissue damage, organ failure and death if not promptly treated.
Another risk factor is premature delivery of the baby, particularly before 32 weeks. This period is so important as during this stage of gestation, the pulmonary surfactant that lines the alveoli, enabling efficient gas exchange, is produced. When babies are born during this period, the likelihood is that their lungs are not properly formed and so they often suffer from breathing difficulties at birth.
Another risk associated with respiratory distress is the delivery of the baby through a caesarean section. This can affect their respiratory health. Often this method of delivery is opted for due to coinciding pregnancy complications such as preeclampsia and breech birth. However, research indicates that elective caesareans also carry with them an increased risk of respiratory distress for the newborn.
Outside of the direct complications associated with the birth event, many studies have shown that babies of the male sex are more likely to suffer from respiratory distress. Furthermore, this effect can be compounded if they are also caucasian. This is an independent risk for the condition too.
This information may come as disconcerting to the expectant parent, however, this knowledge must be understood and circulated so that the risk of respiratory distress developing in each baby can be accounted for and mitigated to the best of the ability of the healthcare team.
References
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- Donda K, Vijayakanthi N, Dapaah-Siakwan F, Bhatt P, Rastogi D, Rastogi S. Trends in epidemiology and outcomes of respiratory distress syndrome in the United States. Pedriatic Pulmonology. 2019 Apr 1; 54(4):405-14.
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- Goldenberg RL, Huddleston JF, Nelson KG. Apgar scores and umbilical arterial pH in preterm newborn infants. American Journal of Obstetrics and Gynecology. 1984 Jul 15; 149(6): 651-4.
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