When a baby arrives before 37 weeks of pregnancy, the journey becomes more complex for families and healthcare providers alike. These tiny fighters face unique challenges as their bodies weren’t fully prepared for life outside the womb, but with proper care and understanding, most premature babies grow into healthy children.
Understanding Premature Birth
A premature baby, often called a “preemie,” is born before completing 37 weeks of pregnancy. While a typical pregnancy lasts around 40 weeks, these infants make their entrance into the world earlier than expected. The timing of birth matters significantly because the final weeks of pregnancy are crucial for the development of vital organs and systems.[1]
Healthcare providers categorize premature births based on how early the baby arrives. Late preterm babies are born between 34 and 36 completed weeks of pregnancy, representing the most common type of premature birth. Moderately preterm infants arrive between 32 and 34 weeks, while very preterm babies are born before 32 weeks. The earliest category, extremely preterm, includes babies born before 25 to 28 weeks of pregnancy.[2][4]
How Common Is Premature Birth?
Premature birth affects families around the world, touching approximately 1 in every 10 births in the United States. The frequency of these early arrivals has been increasing in recent years, partly due to more women becoming pregnant after age 35 and the growing use of assisted reproductive technologies like in vitro fertilization, which often result in multiple pregnancies.[2]
Globally, the scale is substantial. In 2020, an estimated 13.4 million babies were born preterm worldwide, representing more than 1 in 10 of all births. The rate varies considerably by location, ranging from 4% to 16% of babies born in different countries that year. Southern Asia and sub-Saharan Africa account for the majority of preterm births, though this is truly a global concern affecting families everywhere.[4]
Multiple births carry particularly high risk. Almost 60% of twins, triplets, and other multiple deliveries result in preterm births. This significantly contributes to the overall numbers of premature babies requiring specialized care.[3]
Why Babies Are Born Too Early
Most of the time, there isn’t a clear reason why a baby is born prematurely. The cause often remains unknown even after thorough investigation. However, several factors can trigger early delivery or make it more likely to occur.[5]
Sometimes premature birth happens spontaneously without warning. Other times, medical professionals must deliver the baby early due to health complications affecting either the mother or the baby. Medical reasons for early delivery include infections, problems with the placenta such as placental abruption (where the placenta separates from the uterus early) or placenta previa (when the placenta lies too low in the uterus), and conditions like preeclampsia, a serious pregnancy complication involving high blood pressure.[2]
Multiple pregnancies naturally increase the risk of early delivery. The uterus becomes stretched beyond what would occur with a single baby, and the body may respond by initiating labor earlier than expected. Problems with the structure of the uterus or a cervix that cannot stay closed during pregnancy, known as cervical incompetence, can also lead to premature birth.[1]
Chronic health conditions in the mother contribute to risk as well. Diabetes, high blood pressure, heart disease, and kidney problems can all increase the likelihood of premature delivery. Infections affecting the amniotic membranes, vaginal area, or urinary tract pose particular danger because they can trigger early labor.[2]
Who Is at Higher Risk?
Certain groups of women face increased chances of having a premature baby. Age plays a role, with mothers younger than 17 or older than 35 experiencing higher rates of preterm birth. Women who have previously delivered a premature baby or experienced multiple miscarriages or abortions also face elevated risk.[2]
Racial and ethnic disparities exist in premature birth rates. Black and Hispanic women in the United States experience higher rates of preterm delivery compared to other groups, highlighting health inequities that need addressing.[2]
Lifestyle choices during pregnancy significantly impact risk. Smoking cigarettes, drinking alcohol, or using drugs while pregnant increases the likelihood of premature delivery. Poor nutrition, being underweight before pregnancy, or not gaining enough weight during pregnancy also elevates risk.[2]
Women who used in vitro fertilization to become pregnant face higher odds of premature birth, partly because these pregnancies more often involve multiples. Lack of regular prenatal care throughout pregnancy is another risk factor, as problems that could be managed might go undetected and lead to complications requiring early delivery.[5]
Recognizing Premature Babies
Premature babies look noticeably different from full-term infants. Their appearance reflects the interrupted development that would have continued in the womb. The earlier the birth, the more pronounced these differences become.[3]
Size is the most obvious distinction. While a typical full-term baby weighs about 7 pounds, premature newborns might weigh 5 pounds or considerably less. Very premature babies can weigh as little as 1 pound. Their bodies appear small and thin, with heads that look disproportionately large compared to their bodies. This happens because the head grows faster than the rest of the body during pregnancy.[1][3]
The skin of premature babies tells its own story. Without much body fat to cushion and protect them, their skin appears thin, shiny, and almost transparent. Blood vessels may be visible beneath the surface, giving the skin a pink or red appearance depending on how early the baby was born. Fine, downy body hair called lanugo may cover the baby’s back and shoulders. Full-term babies grow and then shed this hair before birth, but premature babies arrive before this process completes.[1][3]
Facial features appear sharper and less rounded than those of full-term babies due to lack of fat cells under the skin. The baby probably won’t have the white, cheesy coating called vernix that protects full-term babies at birth, because this substance isn’t produced until late in pregnancy. Hair on the scalp may be sparse or absent, and the baby’s eyelids may stay closed until reaching about 30 weeks of development.[3][6]
The genitals of both male and female premature babies may appear small and not fully developed. Over time, as the baby grows and matures, these features gradually develop and the baby begins to look more like a typical newborn.[6]
How Premature Babies Behave
Beyond appearance, premature babies act differently than full-term infants. These behavioral differences reflect their immature nervous systems and underdeveloped abilities to regulate their own bodies.[5]
Premature babies often have trouble breathing. Their breathing may be rapid, irregular, or they may experience pauses in breathing called apnea, where they stop breathing for several seconds at a time. This occurs in about half of babies born at or before 30 weeks because the part of the brain controlling breathing hasn’t matured enough to maintain steady respiration.[5]
Maintaining body temperature proves challenging for preemies. Without protective body fat, they get cold quickly even in normal room temperatures. They cannot shiver or take other actions to warm themselves like older children and adults can. This makes keeping them warm a critical priority from the moment of birth.[1]
Feeding difficulties are common because premature babies struggle to coordinate sucking, swallowing, and breathing at the same time. This complex skill normally develops later in pregnancy. Their cries may sound weak compared to full-term babies. They typically sleep more than other newborns but for shorter periods, meaning they wake frequently.[5][10]
Health Challenges Premature Babies Face
Premature babies experience health complications because their organs didn’t have enough time to fully develop before birth. The severity and number of problems typically increase the earlier the baby is born. These complications can affect nearly every system in the body.[5]
Breathing problems top the list of concerns. Many premature babies develop respiratory distress syndrome, a condition where the air sacs in the lungs cannot stay open properly. This happens because the lungs haven’t produced enough surfactant, a slippery substance that keeps the tiny air sacs from collapsing. Without adequate surfactant, the baby struggles to breathe and needs help getting enough oxygen. Some babies develop chronic lung problems from this early respiratory distress.[5]
The brain faces particular vulnerability in premature infants. Weak breathing control, trouble sucking and swallowing, and bleeding in the brain can all occur. These brain complications may lead to long-term problems such as cerebral palsy, a group of disorders affecting movement and posture, or learning difficulties that become apparent as the child grows.[5]
The digestive system may not function properly. Premature babies can develop necrotizing enterocolitis, a serious intestinal problem where tissue in the intestine becomes inflamed and dies. This condition primarily affects preemies and can be life-threatening. Babies with this condition may spit up excessively, have bleeding intestines, and develop yellow skin from jaundice, which occurs when the liver cannot process waste products efficiently.[5][10]
Heart problems occur frequently. A patent ductus arteriosus, a blood vessel that should close after birth but remains open, causes blood to flow incorrectly and diverts it away from the lungs. Blood pressure may be too low or too high, requiring careful monitoring and treatment.[5]
The eyes can suffer damage through a condition called retinopathy of prematurity. This involves bleeding and scarring in the retina, the light-sensitive tissue at the back of the eye. Without treatment, it can lead to vision problems or blindness.[5]
The immune system remains underdeveloped, making premature babies highly susceptible to infections. They lack the antibodies they would have received from the mother in the final weeks of pregnancy. Infections in the bloodstream called sepsis or around the brain called meningitis pose serious threats to these vulnerable infants.[5]
Most complications resolve over time with proper treatment. However, babies who experienced severe complications may continue having problems with breathing, vision, hearing, or development as they grow. Many premature babies catch up to their full-term peers within the first two years of life, though some effects may last longer or become apparent only as the child reaches school age.[5][7]
Special Care in the Hospital
Premature babies need specialized medical attention that begins immediately after birth. Many spend time in a neonatal intensive care unit, commonly called the NICU, which is a specialized nursery designed specifically for sick newborns. The NICU provides an environment that protects the baby from stress while meeting basic needs for warmth, nutrition, and safety to ensure proper growth and development.[3]
Keeping premature babies warm takes priority from the first moments after delivery. They are born into warm towels, dried quickly, and immediately transferred to special equipment designed to maintain their body temperature. Two types of warming devices serve this purpose. An incubator, sometimes called an isolette, is an enclosed bed made of clear plastic that completely surrounds the baby. Temperature inside can be carefully controlled, and the enclosure reduces the chance of infection while limiting fluid loss through the skin. A radiant warmer is an electrically warmed bed that remains open to the air, used when medical staff needs frequent access to provide care. A tiny thermometer taped to the baby’s skin constantly monitors body temperature and helps regulate the heat.[3][10]
Breathing support varies based on the baby’s needs. Some premature infants receive medicine placed directly into their lungs to help them breathe more easily. This medicine often contains surfactant to help the air sacs stay open. Others need a tube placed through the mouth and attached to a breathing machine called a ventilator that helps move air in and out of the lungs. Many babies require oxygen delivered through a mask or through small tubes placed in the nose.[5][8]
Feeding premature babies requires patience and special techniques. Because most cannot nurse or bottle-feed initially, they receive nutrition through tubes. An NG tube, or nasogastric tube, passes milk or nutrition through the nose and into the stomach. Sometimes a G-tube, or gastrostomy tube, is surgically placed through the skin directly into the stomach. In cases where babies cannot tolerate feeding through the stomach at all, they receive complete nutrition through an intravenous catheter in a vein using a solution called total parenteral nutrition or TPN.[10][15]
Breast milk provides the best nutrition for premature babies because it contains proteins that help fight infection. Mothers who cannot breastfeed directly can pump their milk for later feeding. When mother’s milk isn’t available, donor milk from a milk bank provides a safe alternative, or specially designed preterm formulas may be used. Premature babies need more calories, proteins, and other nutrients than full-term babies to support their rapid growth, so extra nutrients called fortifiers may be added to the milk.[10]
Special lights treat jaundice, which appears as yellowing of the skin and occurs frequently in premature babies. These ultraviolet lights help break down the excess bilirubin that causes the yellow color, allowing the baby’s immature liver to process it more easily.[5][8]
Babies stay in the NICU until they can maintain their body temperature in an open crib for 24 to 48 hours, take all feedings without tubes, and steadily gain weight. This process typically takes 2 to 4 weeks but can extend much longer for babies born very early or those who develop complications. Some premature babies remain hospitalized past their original due dates.[10]
Steps to Prevent Premature Birth
While not all premature births can be prevented, several measures significantly reduce the risk. Regular prenatal care stands out as one of the most important protective factors. Attending all scheduled doctor visits throughout pregnancy allows healthcare providers to identify and manage problems early before they lead to complications requiring premature delivery.[8]
Lifestyle choices during pregnancy make a substantial difference. Avoiding all tobacco products, alcohol, and drugs protects the baby from substances that increase premature birth risk. Following a healthy diet and gaining appropriate weight during pregnancy supports the baby’s growth and reduces complications. Women who are underweight before pregnancy or don’t gain enough weight face higher risk of premature delivery.[2]
Managing chronic health conditions carefully throughout pregnancy helps prevent early delivery. Women with diabetes, high blood pressure, heart disease, kidney problems, or other ongoing health issues should work closely with their healthcare providers to keep these conditions well-controlled during pregnancy. Treating infections promptly, especially urinary tract infections, vaginal infections, and other infections that could affect the pregnancy, reduces the risk of premature labor.[2]
For women who go into labor prematurely, doctors may prescribe medicine to slow down labor and give the baby more time to develop in the womb. They may also give the mother medicine to help the baby’s lungs develop faster, which can greatly improve outcomes if early delivery cannot be prevented.[8]
How Prematurity Affects the Body
Understanding what happens inside a premature baby’s body helps explain why they face so many challenges. The final weeks of pregnancy involve rapid maturation of organs and systems that prepare the baby for independent life. When birth comes early, this preparation remains incomplete.[2]
The lungs represent perhaps the most critical system affected by prematurity. In the womb, babies don’t breathe air because they receive oxygen through the umbilical cord. Lung development accelerates in the final weeks of pregnancy, when special cells begin producing surfactant. This slippery substance coats the inside of the air sacs, allowing them to remain open and expand with each breath. Without sufficient surfactant, the air sacs collapse, making breathing extremely difficult and inefficient. The baby must work much harder to breathe, and getting enough oxygen becomes a struggle.[1]
The brain’s immaturity affects multiple functions. The respiratory center in the brainstem, which controls the rhythm of breathing, may not work smoothly. This leads to irregular breathing patterns and episodes where breathing stops temporarily. The areas controlling sucking, swallowing, and coordination of these actions with breathing remain underdeveloped, explaining feeding difficulties. Blood vessels in the brain are fragile and can bleed easily, potentially causing lasting damage.[5]
The digestive system faces mechanical and functional challenges. The intestines have thin, delicate walls that can become inflamed and damaged. The stomach may not empty properly, leading to feeding intolerance. The liver’s ability to process waste products, particularly bilirubin, lags behind what’s needed, resulting in jaundice. Muscles controlling digestion and movement of food through the intestines work inefficiently.[5]
The heart may continue functioning as it did in the womb rather than adapting to life outside. Before birth, a blood vessel called the ductus arteriosus allows blood to bypass the lungs because the baby receives oxygen through the umbilical cord. This vessel normally closes shortly after birth, redirecting blood to flow through the lungs to pick up oxygen. In premature babies, it often stays open, causing blood flow problems and making the heart work harder.[5]
Blood vessels in the eyes develop abnormally when exposed to the outside environment too early. The retina hasn’t finished forming its complete network of blood vessels. The growth process can go wrong, with vessels growing in disorganized patterns that can pull on the retina, potentially causing detachment and vision loss if not treated.[5]
The immune system lacks maturity and readiness to fight infections. Premature babies haven’t received the full complement of antibodies from their mothers that would normally transfer across the placenta in late pregnancy. Their own immune systems haven’t developed the ability to recognize and respond to invading bacteria and viruses effectively. This leaves them vulnerable to infections that could be life-threatening.[5]
Body temperature regulation fails because multiple systems remain immature. Premature babies have minimal body fat for insulation, thin skin that allows heat to escape easily, and immature reflexes for conserving heat. They cannot shiver to generate warmth or constrict blood vessels to reduce heat loss. Even the metabolic processes that generate heat as a byproduct work less efficiently than in full-term babies.[1]