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Modern Medicine Has Transformed Preterm Birth But We Still Have a Long Way to Go

Skin so translucent and fragile it tears like tissue paper. Faces obscured by oxygen masks. Alarms going off very few minutes. Bassinets covered in plastic wrap. 

This is the world of babies born extremely preterm—at less than 28 weeks of pregnancy. Yet for all the almost sinister machines surrounding these tiny humans–tubes and incubators, oxygen masks and respirators–they represent a medical “miracle”.

Just 40 years ago, birth before 28 weeks, a full twelve weeks early, was a death sentence. When Jackie Kennedy went into labor 6 weeks early in 1962, doctors gave her preemie son, Patrick Bouvier, a 50-50 shot at survival. 

With the nation watching, Patrick’s condition deteriorated rapidly. He lived for just 39 hours, dying from Respiratory Distress Syndrome,  a lung condition which remains common among premature babies.

In low-income countries, babies born at 34 weeks like Patrick Bouvier continue to face only a 50-50 shot at survival. 

But in developed countries, like most of Western Europe and the United States, the age at which most babies survive, sometimes known as the age of viability, has crept earlier and earlier. Today, just over a third of babies born at 23 weeks, and over half of those born at 24 weeks, will survive. A baby born at 28 weeks has nearly a 90% chance of survival. Babies born at 34 weeks have survival rates topping 99%

Yet, preterm birth is by no means “solved”. Even in the U.S., it remains the second leading cause of death in children under the age of 5, and contributes to roughly half of all childhood disabilities

This medical “miracle” also presents one of medicine’s most intractable problems. 

preemie and baby born at 28 weeks preterm birth

How Modern Medicine Transformed Preemie Survival

When it comes to boosting survival, nearly all of recent medical advances involve the lungs. 

Understanding Fetal Lung Development

Inside the womb, the lungs are useless. The baby swims in a fluid filled sac, which contains no air. 

For this reason, the fetal heart bypasses the fetal lungs altogether. Blood carrying oxygen passes from the mother through the placenta and umbilical cord directly to the fetal heart, where it is pumped throughout the body. 

Then everything changes. The moment after birth, this bypass closes. The baby is suddenly cut off from mom’s blood supply, and her lungs must begin taking in oxygen to sustain life. 

To enact this dramatic switch—from passively receiving oxygen to extracting it from the air—the lungs undergo a series of critical preparatory steps while in the womb.


The moment after birth, the baby is suddenly cut off from mom’s blood supply, and her lungs must begin taking in oxygen to sustain life. 


In the second trimester, the fetus begins practicing breathing, “inhaling” and “exhaling” amniotic fluid. Then, around 24 weeks, of pregnancy the lungs begin to coat themselves with a mixture of carbohydrates, proteins, and fats known as surfactant. 

Surfactant is critical for breathing air. It decreases surface tension inside the lungs. Without it, the lungs will collapse when exhaling air.

Lung development the main reason very few babies born before 23 weeks survive, but the majority born after 24 weeks do. This window of time represents a critical juncture. These weeks are when the fetal lungs become able to take in oxygen, release carbon dioxide, and produce surfactant. 

Medical Advances Boosting Preemie Survival

In the 1980s, doctors developed machines that could force air into preemies’ lungs, which provided babies who could not breathe on their own with life-sustaining oxygen. 

In the 1990’s, continuous air pressure devices to aid breathing and artificial surfactant given after birth spurred further increases in survival, especially among the very youngest preemie. Doctors of the ’90’s also began to give women, at risk of premature delivery, steroids to hasten fetal lung development. A single dose of steroids at least 24 hours before birth dramatically raises the chances of preemie survival. It also lowers the risk of major complications like respiratory distress syndrome and bleeding in the brain.

But the timing of these steroids is key. Given too close to delivery, they do not have sufficient time to boost lung development. Given too early, on the other hand, and their beneficial effects fade. The ideal is between 1-7 days before birth

Complicating matters is the fact that, ideally, steroids are given only once. Multiple doses have been linked with poorer long-term cognitive outcomes.

preemie baby born at 28 weeks preterm birth

Lungs = survival… with health complications. So now what?

Despite survival rates rising dramatically, the rates of major complications have remained stubbornly high. Extremely premature babies face serious physical challenges. They face much higher risks of cerebral palsy, blood and brain infections, blindness, deafness, brain bleeds, and respiratory distress syndrome (RDS) than babies born full-term. They also are more prone to mental challenges, suffering elevated rates of ADHD, autism, and developmental delays.

Researchers are testing multiple treatments that may eventually improve preemies’ long-term health, such as administering antioxidants and anti-inflammatory medications. 

Yet, more than any likely medical advance, the most dramatic improvements might simply come from more time inside the womb. 

A baby born at 23 weeks has a less than 1 in 10 chance of survival without any major disability, such as blindness, deafness, or severe cerebral palsy. These dire odds, however, improve rapidly with each extra week inside the womb. By 25 weeks of pregnancy, a baby’s chances of avoiding a major disability has more than doubled to 1 in 3. By 27 weeks, it is an odds on bet

So why aren’t we doing everything possible to grant these fragile babies more time in the womb? 

Right now, medicine cannot yet accurately predict when labor will start, nor stall labor once it has begun. Current labor-delaying drugs like magnesium sulfate can hold off labor by at most a few precious days. These extra hours are invaluable. They allow time to transfer to a hospital with a specialized neonatal intensive care units (NICU) and to treat mothers with steroids to speed up fetal lung development. But the extra time inside is not long enough to give these preemies the best shot at a full, healthy life.


Why aren’t we doing everything possible to grant these fragile babies more time in the womb? 


Imagine if we solved this puzzle. Consider the dramatic impact of being able to stall labor by a week or more. One week or even two weeks seems like a mere drop in the bucket of a lifetime, but it is a vast span of time for a fetus. The difference in the health outcomes for a preemie born at  23 weeks and those born at 25 weeks is enormous. In one fell swoop, we could significantly lower preemies’ risk of severe disabilities. Such an advance could transform the lives of preemies and their families. 

Thus far, none of medicine’s major advances come close to more time in the womb.

In the fight to solve premature birth, let’s not lose sight of the value of incremental progress—how every extra day, every extra week, has value to women and their babies. 

At Bloomlife, we honor those who put women first, those working to better understand pregnancy and the causes of preterm birth, and those who value every single week. See how you can get involved today.


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About Amy

Amy Kiefer is a researcher by training, and earned her Ph.D. from the University of Michigan. She currently lives in the Bay Area with her husband and three children where she writes about fertility, pregnancy, and breastfeeding. Check out her blog,, for more great evidence-based pregnancy and parenting info.


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