Respiratory distress syndrome (RDS) is a breathing condition that primarily affects premature babies whose lungs haven’t yet produced enough surfactant, a slippery coating that keeps the tiny air sacs in the lungs from collapsing. It is the most common respiratory problem in preterm infants. Nearly 98% of babies born at 24 weeks develop RDS, while at 34 weeks the rate drops to about 5%, and by 37 weeks it falls below 1%. With modern treatment, including surfactant therapy and breathing support, survival rates exceed 90% and can reach as high as 98%.
Why Surfactant Matters
Your lungs contain millions of tiny air sacs called alveoli. Each time you breathe out, these sacs need to stay partially open so they can fill again on the next breath. Surfactant is a mixture of fats and proteins that coats the inside of these sacs and lowers their surface tension, much like soap reduces the tension in a water bubble. Without it, the air sacs collapse on themselves after each exhale, making it progressively harder for the baby to inflate them again.
Surfactant production begins around 26 weeks of pregnancy and reaches mature levels at roughly 35 weeks. Babies born before that window often don’t have enough surfactant to keep their lungs open, which leads to stiff lungs, poor oxygen exchange, and the cascade of symptoms that define RDS. The condition is sometimes called hyaline membrane disease, a name that comes from the protein-rich membrane that forms inside damaged air sacs.
Who Is at Risk
Prematurity is the single biggest risk factor. The earlier a baby is born, the less surfactant is available and the higher the chance of RDS. But gestational age isn’t the only factor. Male infants are at higher risk than females at the same gestational age. Delivery by cesarean section also increases risk, likely because the hormonal surge and chest compression of vaginal birth help clear fluid from the lungs.
Maternal diabetes, whether gestational or pre-existing, is an increasingly recognized contributor. High insulin levels in the fetus can delay surfactant maturation, which means even babies born at full term to mothers with diabetes face elevated risk. One large meta-analysis found that maternal gestational diabetes raised the odds of RDS by about 60% in term infants and 80% in preterm infants. Other risk factors include oxygen deprivation during birth and having a sibling who had RDS.
Signs That Appear at Birth
RDS typically shows up within the first few hours of life, often within minutes of delivery. The hallmark signs include:
- Fast, shallow breathing as the baby works harder to get air into stiff lungs
- Grunting on each exhale, caused by the baby partially closing the back of the throat to try to keep air sacs from collapsing
- Nasal flaring with each breath
- Chest retractions, where the skin pulls inward between or below the ribs during breathing
- Bluish tint to the skin and lips from low oxygen levels
These symptoms tend to worsen over the first day or two, then gradually improve by day three or four as the baby’s lungs begin producing their own surfactant and excess fluid clears.
How RDS Differs From Similar Conditions
Several other newborn breathing problems can look similar, so clinicians use chest X-rays, timing, and risk factors to tell them apart.
Transient tachypnea of the newborn (TTN) is the most common mimic. It happens when fluid that normally fills a baby’s lungs before birth isn’t absorbed quickly enough after delivery. TTN causes rapid breathing and some increased effort, but it typically resolves within 24 to 72 hours and rarely requires a breathing machine. On X-ray, TTN shows fluid in the lung tissue and sometimes between the lobes, whereas RDS appears as a uniform, grainy haziness with low lung volumes.
Meconium aspiration syndrome occurs when a baby inhales stool-stained amniotic fluid before or during birth. The bile acids in meconium actually inactivate surfactant, so X-rays can sometimes resemble RDS. But meconium aspiration more often produces overinflated lungs with patchy areas of collapse, and it almost exclusively affects full-term or post-term babies rather than preemies. Neonatal pneumonia can be nearly indistinguishable from RDS on imaging, which is why antibiotics are often started alongside RDS treatment until infection is ruled out.
Surfactant Replacement Therapy
The cornerstone of RDS treatment is giving the baby surfactant directly into the lungs. This replaces what the baby can’t yet make on its own and dramatically improves lung function, often within minutes. Most surfactant preparations used today are derived from animal lungs (bovine or porcine). Studies comparing the two have found that porcine surfactant tends to be slightly more effective at reducing mortality and the need for repeat doses.
How the surfactant gets into the lungs has evolved significantly. The traditional approach involved inserting a breathing tube, delivering the surfactant, and then removing the tube and placing the baby on gentler breathing support. This sequence is known by the acronym INSURE (intubate, surfactant, extubate). Newer techniques aim to skip the breathing tube entirely. One method called LISA (less-invasive surfactant administration) threads a thin, flexible catheter into the airway while the baby continues breathing on nasal pressure support. Another uses a small mask placed over the back of the throat. Researchers are also working on delivering surfactant as an inhaled mist, which would be the least invasive option of all.
Breathing Support
Beyond surfactant, most babies with RDS need help keeping their lungs inflated. The preferred first-line approach is nasal continuous positive airway pressure, or CPAP, which delivers a steady stream of pressurized air through small prongs in the nose. CPAP keeps the air sacs from collapsing between breaths without requiring a tube in the windpipe.
Clinical trials comparing early CPAP to immediate placement on a mechanical ventilator have shown that CPAP is a safe and effective alternative. In one study, only 32% of very small infants started on CPAP eventually needed to be switched to a ventilator. Current guidelines from the American Academy of Pediatrics recommend starting with CPAP whenever possible, because avoiding mechanical ventilation reduces lung injury and lowers the risk of chronic lung problems down the road. When a baby does need a ventilator, clinicians aim to transition back to CPAP as soon as the baby can sustain adequate breathing on less support.
Prevention Before Birth
The most effective way to reduce the severity of RDS is to accelerate lung maturation before the baby is born. When preterm delivery is expected within the next seven days, the mother receives a course of corticosteroid injections. These medications cross the placenta and trigger the baby’s lungs to ramp up surfactant production ahead of schedule.
Current guidelines from the American College of Obstetricians and Gynecologists recommend this treatment for pregnancies between 24 and 34 weeks of gestation, with consideration as early as 23 weeks depending on the family’s wishes about resuscitation. A later course between 34 and 37 weeks is also recommended if the mother hasn’t received steroids before. The peak benefit occurs two to seven days after the first injection, though even a single dose given less than 24 hours before delivery significantly reduces complications. If more than 14 days have passed since the original course, a single repeat course can be considered if preterm delivery still looks likely.
Possible Complications
Most babies with RDS recover fully, but the condition and its treatment can lead to longer-term problems, particularly in the smallest and most premature infants. Bronchopulmonary dysplasia (BPD) is a form of chronic lung disease that develops when immature lungs are injured by inflammation, oxygen exposure, and mechanical ventilation. Babies with BPD may need supplemental oxygen for weeks or months after leaving the hospital, and some experience breathing difficulties into childhood.
Retinopathy of prematurity (ROP) is another concern. The blood vessels supplying the retina aren’t fully formed in very preterm infants, and abnormal vessel growth can occur, potentially leading to vision problems or, in severe cases, retinal detachment and blindness. When BPD and severe ROP occur together, the combination is associated with poorer developmental outcomes even in children without obvious brain injury. These risks underscore why minimizing ventilator time and oxygen exposure is a central goal of modern neonatal care.