What Is RDS in Babies? Signs, Diagnosis & Treatment

Respiratory distress syndrome (RDS) is a breathing disorder that primarily affects premature babies whose lungs have not yet produced enough surfactant, a slippery substance that keeps the tiny air sacs in the lungs from collapsing. It is the most common serious lung condition in preterm infants and typically appears within minutes to hours after birth. The condition has gone from being frequently fatal a few decades ago to highly treatable today, but it still demands rapid recognition and skilled neonatal care. Understanding how RDS develops, what to watch for, and what treatments are available can help parents feel less in the dark during a frightening NICU stay.

Why RDS Happens

The root cause of RDS is straightforward: not enough surfactant. Surfactant is a mixture of fats and proteins produced by specialized cells in the lungs called type II cells. It coats the inner surface of each air sac and reduces surface tension, which is what allows the sacs to stay open when a baby exhales. Without it, the air sacs collapse after every breath, and the baby has to work enormously hard just to re-inflate them with each new breath.

Type II cells begin appearing and producing surfactant around 24 weeks of gestation, but only in tiny amounts. Production ramps up dramatically between roughly 28 and 34 weeks, and by about 34 to 36 weeks, most babies have enough surfactant to breathe comfortably on their own.¹ One study tracking surfactant protein in fetal lung tissue found that the number of surfactant-producing cells jumped sharply between 27 and 28 weeks, then continued climbing through 33 weeks, with widespread surfactant spread across the air sacs from 34 weeks onward.² This timeline explains why RDS is overwhelmingly a disease of prematurity: the earlier a baby is born, the less surfactant is available, and the more severe the breathing trouble tends to be.

Recognizing the Signs

RDS usually shows itself within the first few hours of life. The hallmark signs are rapid breathing, flaring of the nostrils with each breath, visible pulling-in of the skin between the ribs or below the breastbone (called retractions), and a distinctive grunting sound on exhale. That grunting is actually the baby’s body trying to keep the air sacs from collapsing by pushing air out against a partially closed airway.³ If these symptoms are not caught and managed quickly, the baby can progress into full respiratory failure with blue-tinged skin (cyanosis) and dangerously low oxygen levels.

In very premature babies, the signs may be obvious from the first breaths. In late-preterm infants born closer to 36 weeks, the onset can be subtler and may initially be mistaken for a less serious condition called transient tachypnea of the newborn, which resolves on its own. That distinction matters a great deal for treatment decisions, which is why the NICU team watches breathing patterns, oxygen requirements, and chest imaging closely in the hours after delivery.

Who Is Most at Risk

Gestational age is the single biggest predictor. The earlier a baby arrives, the higher the risk. But gestational age is not the only factor. Several other characteristics increase the likelihood of RDS:

Male sex: Boys are consistently more likely to develop RDS than girls at the same gestational age, a finding confirmed in studies spanning early preterm through full-term births.⁴ ⁵
Low birth weight: Smaller babies at any gestational age face higher risk.
Cesarean delivery (especially scheduled): Elective cesarean section without labor skips the hormonal surge that helps clear fluid from the lungs and stimulates surfactant release. Both elective and emergency cesarean sections have been identified as risk factors for RDS.⁴
Gestational diabetes: Maternal diabetes, even when well-managed, can delay lung maturation.⁵
Low Apgar scores: A score below 7 at five minutes after birth signals a rocky transition and is independently linked to RDS.
Maternal complications: Conditions such as antepartum hemorrhage and prolonged rupture of membranes have been associated with increased risk of RDS in preterm neonates.⁶
Advanced maternal age: Older mothers face a modestly higher chance of having an infant with RDS.⁴

Some of these factors are modifiable and some are not, but knowing them helps clinicians prepare. When a very premature delivery is anticipated, the medical team can take preventive steps before the baby even arrives.

Prevention Before Birth

The most effective way to reduce the severity of RDS is to give the mother corticosteroid injections before delivery. These steroids cross the placenta and speed up surfactant production in the baby’s lungs. A Cochrane systematic review, one of the most rigorous forms of evidence synthesis available, confirmed that a single course of antenatal corticosteroids reduces the risk of RDS, neonatal death, and perinatal death in women at risk of preterm birth.⁷ This intervention has become standard practice worldwide for pregnancies threatening to deliver before 34 weeks.

There is also evidence that a single dose of betamethasone given between 34 and 36 weeks to women likely to deliver early can reduce both the need for resuscitation and the rate of RDS in late-preterm infants.⁸ For parents hearing that their baby may come early, the steroid injections are often one of the first interventions discussed, and they remain the single biggest tool for preventing severe RDS.

How RDS Is Diagnosed

Diagnosis typically combines what the clinician sees at the bedside with imaging. The clinical picture of a premature infant grunting, retracting, and needing increasing amounts of oxygen shortly after birth is suggestive on its own. A chest X-ray has traditionally been the go-to confirmation tool. On X-ray, RDS shows a characteristic “ground-glass” appearance with air-filled tubes (air bronchograms) visible against the opaque, fluid-filled lung tissue.

That said, the role of chest X-ray is being re-evaluated. A systematic review of 23 studies found that while about a third of the studies called chest X-ray irreplaceable for diagnosing RDS, nearly half found that alternative methods outperformed it in several respects, including assessing severity, predicting whether surfactant therapy would be needed, and guiding decisions about intubation.⁹ Lung ultrasound is the leading contender. It is portable, avoids radiation, and can be performed right at the incubator. Ultrasound can distinguish RDS from transient tachypnea of the newborn by looking for specific patterns: lung consolidation with air bronchograms points to RDS, while a different pattern called the “double lung point” is characteristic of transient tachypnea.¹⁰

Blood markers are also being explored as additional diagnostic tools. Research has found that babies with RDS tend to have higher levels of the enzyme LDH and elevated inflammatory markers compared to those with transient tachypnea, and that an LDH level above a certain threshold can help distinguish the two conditions.¹¹ These are not yet routine in most NICUs, but they represent the direction diagnosis is heading, especially in settings where advanced imaging is not readily available.

Treatment With Surfactant

The introduction of synthetic and animal-derived surfactant in the 1980s transformed RDS from a leading cause of infant death into a condition with a dramatically better prognosis. Surfactant replacement therapy remains the cornerstone of treatment. The medication is delivered directly into the lungs, where it does what the baby’s own surfactant should have been doing: lowering surface tension and keeping the air sacs open.¹²

Timing matters. Early rescue surfactant, given as soon as it becomes clear the baby has worsening RDS, produces better results than waiting.¹³ Prophylactic surfactant given immediately to every premature baby at birth was once routine, but it has fallen out of favor now that non-invasive breathing support can be started first. Many babies stabilize on CPAP alone and never need surfactant at all, which avoids the risks of intubation.

When surfactant is needed, more than one dose is often better. A meta-analysis comparing multiple versus single doses found that giving additional doses led to better oxygen levels, a lower risk of pneumothorax (air leaking out of the lung), and a trend toward improved survival, with no additional complications reported from the extra doses.¹⁴

Breathing Support Beyond Surfactant

Surfactant addresses the underlying chemical problem, but most babies with RDS also need help keeping their airways pressurized. The standard first-line approach today is continuous positive airway pressure, or CPAP, delivered through small prongs or a mask at the nose. CPAP provides a gentle, constant flow of pressurized air that keeps the air sacs partially inflated so the baby does not have to reinflate them from scratch with every breath. In resource-limited settings, CPAP alone has been associated with roughly halving the need for mechanical ventilation.¹⁵

A step above CPAP is nasal intermittent positive pressure ventilation, or NIPPV, which adds periodic puffs of higher pressure on top of the baseline CPAP. Meta-analyses have found that NIPPV is better than CPAP alone at preventing respiratory failure and the need for intubation, and it is associated with lower rates of chronic lung disease.¹⁶ When non-invasive support is not enough, mechanical ventilation through a breathing tube remains available, though clinicians now try hard to avoid it or minimize its duration because of the lung injury it can cause.

Less Invasive Surfactant Delivery

One of the biggest shifts in neonatal care over the past decade has been the push to deliver surfactant without putting a breathing tube into the baby’s windpipe. The most widely adopted method, called LISA (less invasive surfactant administration), involves threading a thin, flexible catheter through the vocal cords and dripping surfactant into the lungs while the baby stays on CPAP and continues breathing spontaneously. Randomized studies and meta-analyses show that LISA helps avoid mechanical ventilation and is linked to lower rates of both chronic lung disease and bleeding in the brain compared to traditional intubation-based surfactant delivery.¹⁷

Even LISA still requires a laryngoscope, which is uncomfortable for the baby. Researchers are working on the next frontier: delivering surfactant as a nebulized mist through the CPAP circuit, so no instrument enters the airway at all. Animal studies and early human trials have shown this approach is safe and potentially effective, though optimizing the technology for consistent dosing remains a work in progress.¹⁸

Complications Parents Should Know About

RDS itself is treatable, but it can set the stage for secondary problems, some immediate and some longer-term.

In the short term, the low oxygen levels caused by RDS can keep a blood vessel called the ductus arteriosus from closing. This vessel normally shuts on its own shortly after birth, but in babies with RDS, it often stays open, creating a condition called patent ductus arteriosus (PDA). A PDA allows blood to flow in an abnormal loop that floods the lungs with extra blood, worsening the oxygen situation.¹⁹ Some babies with a significant PDA require medication or surgery to close it.²⁰ Pneumothorax, where air leaks out of a damaged air sac and accumulates around the lung, is another acute complication, occurring more frequently in babies with severe RDS.²¹

The most significant long-term complication is bronchopulmonary dysplasia (BPD), a form of chronic lung disease. BPD was originally described as the scarred, fibrotic endpoint in babies who survived severe RDS after prolonged exposure to high oxygen concentrations and positive-pressure ventilation.²² Today’s “new BPD” looks somewhat different because babies are managed more gently, but premature infants treated for RDS remain at elevated risk of developing it.²³ BPD can mean persistent breathing difficulties, increased vulnerability to respiratory infections in early childhood, and sometimes a need for supplemental oxygen at home after hospital discharge.

Eye Problems Linked to RDS

Retinopathy of prematurity (ROP), a condition where abnormal blood vessels grow in the retina and can threaten vision, is a known risk for premature babies. RDS appears to add to that risk independently. A large population-based study in Taiwan found that the rate of ROP was roughly two and a half times higher in infants with RDS than in matched premature infants without it. The association was especially strong in babies with normal or near-normal birth weights, where infants with RDS had more than three times the rate of ROP compared to controls. Among babies with RDS who required invasive ventilation or stayed in the NICU for 30 days or longer, the incidence climbed further still.²⁴

The mechanism likely involves the fluctuating oxygen levels that accompany RDS and its treatment. Immature retinal blood vessels are extremely sensitive to swings between too little and too much oxygen. This is one reason NICU teams carefully monitor oxygen saturation targets, trying to keep levels in a narrow band that supports the baby without overdoing it. Parents can expect their baby’s eyes to be screened by a pediatric ophthalmologist at set intervals during and after a NICU stay, and most mild cases of ROP resolve without treatment as the baby matures.

RDS in Late-Preterm and Term Infants

Most discussions of RDS focus on very premature babies, but the condition can occur in late-preterm infants (34 to 36 weeks) and even occasionally at full term. In these cases, lung maturity may be compromised by gestational diabetes, scheduled cesarean delivery before labor begins, or genetic variants that affect surfactant production. A multi-center study of infants born between 34 and 42 weeks confirmed that low Apgar scores, male sex, and gestational diabetes were independent risk factors for RDS even in this older group.⁵

RDS in near-term babies tends to be milder and respond well to treatment, but it catches families off guard because they were not expecting NICU complications at that stage of pregnancy. The diagnosis can also be trickier, since transient tachypnea of the newborn presents similarly and is far more common at these gestational ages. A one-day-old baby breathing fast after a scheduled C-section might have either condition, and clinicians use imaging, oxygen trends, and sometimes lab markers to distinguish them.²⁵

Outcomes in Resource-Limited Settings

RDS outcomes vary enormously depending on where a baby is born. In high-income countries with well-equipped NICUs, the survival rate for even very premature infants with RDS is high. In resource-limited settings, the picture is different. Survival among infants born before 32 weeks has historically been below 50% in low-resource environments, though increased access to basic interventions like CPAP has pushed this closer to 70% in many areas.¹⁵

The barriers are not only about money. Surfactant is expensive and requires cold-chain storage. CPAP machines, while simpler than ventilators, still need reliable electricity and trained staff. Chest X-ray may be the only imaging modality available in some facilities, while lung ultrasound, which is arguably more useful for RDS, requires a different set of training. Research into diagnosis in low-resource birth scenarios has explicitly examined how best to use the tools that are actually available, rather than assuming every hospital has a fully stocked NICU.⁹ For global child health, making even basic RDS care more accessible remains one of the most impactful ways to reduce newborn deaths.

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