Premature Birth and Preterm Labor Defined
The average full-term pregnancy lasts 40 weeks. A premature birth—or preterm birth—is a birth that occurs before 37 weeks of pregnancy are complete.
Preterm labor is labor that starts before the end of the 37th week. Preterm labor can be spontaneous (happening on its own) or because the healthcare team starts preterm labor for the health of the mother or the baby. In the US, about one of every 10 babies is born too early. There are three main levels of prematurity, based on how early the baby is born.
What is Gestational Age?
In order to understand what is considered premature birth, it’s important to understand gestational age. Gestational age is the number of weeks and days of your pregnancy. For example, if you are on the 5th day of your 20th week of pregnancy, you are at “20 5/7 weeks.” At your first prenatal visit, your doctor will help you figure out your due date based on the start of your last period. They will confirm the baby’s due date with an ultrasound. The due date is used to calculate the gestational age of your baby. To learn more about ultrasound and other tests performed during pregnancy, check out this blog post about routine prenatal tests.
Categories of Preterm Birth
There are three main levels of preterm birth based on the gestational age of the baby. These are:
- Moderate or late preterm: premature birth between 32 and 37 weeks
- Very preterm: premature birth between 28 and 32 weeks
- Extremely preterm: premature birth before 28 weeks
While every preterm baby is unique, these categories are useful for understanding the types of problems that certain preemies may face, based on how early they were born.
Characteristics of a Premature Baby
The characteristics of a premature baby differ according to their overall health, the number of babies in the pregnancy (like single babies, twins, triplets, or more), and their gestational age. While many late preterm babies may look like small-sized newborns, those born earlier will be very small and look more fragile than a typical newborn baby.
The size of a premature infant depends on their gestational age and many other pregnancy factors, but many preemies are considered to be “low birth weight,” or weighing less than five and a half pounds.
Here are some of the other traits that premature babies often have:
- Eyelids may be closed until the baby reaches about 30 weeks of gestational age
- A lack of hair on the head with the presence of soft body hair called lanugo
- Shiny, reddish, or translucent skin
- A thin body, with a large head compared to the rest of the body
- A weak sounding cry
- Genitals that are small and not fully developed
- A tendency to sleep more than full-term babies
Short-Term Health Problems for Preterm Babies
Premature babies face many short-term health issues. These are some of the most common problems of prematurity that doctors treat in the first few days, weeks, and months of a child’s life:
- Difficulty maintaining body temperature. Fat stores that develop late in pregnancy help babies maintain a healthy body temperature. Because preemies are missing this fat, they are less able to maintain their temperature without help.
- Issues with breastfeeding and bottle feeding. Preterm babies usually need to eat more frequently than full-term babies, and it can be hard for them to learn to suck and swallow. Some preemies have poor digestion. They may develop problems like necrotizing enterocolitis, a disease of the intestine.
- Problems with breathing. A premature baby faces several types of breathing problems, like infant respiratory distress syndrome and sleep apnea (stopping breathing).
- Higher risk for infections. Premature babies have not had a chance to develop their immune systems, so they have a harder time fighting off germs than full-term babies do.
- Heart and circulation problems. Some preterm infants have patent ductus arteriosus, a condition that sends blood away from the lungs. They may also have health problems related to high or low blood pressure or a low heart rate.
- Kidney and liver problems. Jaundice can occur in babies with immature livers. Kidneys may not be fully developed at birth in a premature baby.
- Blood issues. Some premature babies have anemia, an illness caused by a lack of healthy red blood cells. Early labor can also result in an imbalance in minerals and other substances in their blood.
- Brain and nervous system problems. Some preterm babies have brain bleeding, seizures, or retinopathy (a disease of the eye) as a result of an extremely preterm birth.
Long-Term Health Complications for Premature Babies
Preterm babies have a higher risk for long-term health problems than babies who reach a full term pregnancy. There are several types of medical issues and health problems that a premature birth baby can face as they grow up:
- Cerebral palsy
- Vision loss
- Hearing loss
- Intellectual/learning problems
- Mental health issues
- High blood pressure
- Long-term lung problems
Survival of Preterm Babies
Advances in medical care mean that more and more premature babies are able to survive. A recent US report found that the survival rate for extremely preterm babies born between 22 and 28 weeks increased to 78% in 2018, up from 76% in 2012.
The longer a baby is able to stay in the womb, the higher their chances of living. In the same study, 94% of premature babies born at 28 weeks survived to leave the hospital, compared to only 11% of those born at 22 weeks.
Special Care for Preterm Babies
Preterm babies need special care in the hospital before they can go home with their parents. Extremely preterm babies—those born before 28 weeks—face special challenges. The American College of Obstetricians and Gynecologists has a useful FAQ page about caring for extremely preterm children and the problems of premature birth.
While every baby’s needs are unique, here are some of the common treatments preterm babies receive before at the hospital:
- Temperature maintenance. Warming beds called incubators help preemies maintain the correct body temperature.
- Measuring vital signs. Healthcare providers will keep track of baby’s temperature, blood pressure, heart rate, breathing rate, and blood oxygen levels.
- Oxygen. Premature birth often includes special care such as giving extra oxygen when needed.
- Intravenous (IV) fluids. IVs provide extra fluids and medicine for the health of babies who need them.
- Feeding. Babies born prematurely usually need help with special feedings. At first, breast milk or formula is given through a tube in the stomach for babies that can’t yet suck and swallow.
If your baby is born early, your baby’s doctor will develop a care plan that’s just right for them. While late preterm babies who do not have serious health problems can be treated in a special care nursery, babies who are born on the earlier side will need to spend time in a more specialized care center. The American Academy of Pediatrics has described four levels of newborn (neonatal) care. Doctors who specialize in caring for newborns are called neonatologists.
Well Newborn or Level I Neonatal Unit
A Level 1 neonatal unit is a nursery that provides basic care for newborns. The nursery can also provide immediate help to stabilize sick or premature babies to get them ready to move into a higher level nursery.
Special Care Nursery or Level II Neonatal Unit
A Special Care Nursery (or Level II neonatal unit) gives premature birth babies additional care they wouldn’t be able to get in a well newborn nursery. They can take care of moderately sick newborns or preemies who are born at 32 weeks of pregnancy or later and who weigh 3.3 lbs. or more. They can provide help with feeding and mild breathing problems. In many cases, babies who grow and become stable in a higher-level unit can continue their care in a Special Care Nursery until it’s time to go home.
Neonatal Intensive Care Unit (NICU) or Level III Neonatal Unit
A NICU, or Level III Neonatal Intensive Care Unit, provides a higher level of care for very ill full-term babies and for those who are born before 32 weeks gestation and/or who weigh less than 3.3 lbs. NICUs are run by neonatologists who work with a team to give advanced breathing treatments, high-level testing, and life support, along with special feeding and other care for extremely premature babies.
Regional NICU or Level IV Neonatal Unit
Regional NICUs (or Level IV units) have all the capabilities of a NICU and are also located at a hospital that can perform surgery for babies who need it. Regional NICUs have neonatologists on staff, as well as subspecialists like neonatal anesthesiologists and surgeons.
Going Home After Special Preterm Birth Care
How Long Do Preemies Stay in the Hospital?
Many factors play into the length of a hospital stay for a premature baby. Extremely preterm birth babies will need a longer time to grow and overcome health problems, while later preterm babies usually have shorter stays. In general, many doctors give parents a guide of the baby’s original due date as a target for going home. But before they go home, preterm babies will need to breathe on their own, be able to eat without problems, keep gaining weight, and be able to maintain their own body temperature.
Special Care After the Hospital
Many preemies still require special care after they go home. Premature babies may need extra oxygen, special tube feeding, or medicine. The hospital healthcare team works closely with parents to make sure they have all the tools and skills they need to care for their baby at home.
Prevention Strategies for Preterm Babies
Even with the best possible special care available for premature babies, experts agree that the best place for babies to grow and thrive is in the womb. Preventing preterm birth is not always possible, but there are several steps you can take during pregnancy to ensure that your baby has the best start in life. Some of the most important keys to staying healthy and preventing preterm labor include:
- Keeping up with prenatal care
- Getting treatment for chronic health conditions
- Avoiding infections while pregnant
- Stopping the use of tobacco, alcohol, and illegal drugs during your pregnancy
- Learning your risk of preterm labor early in your pregnancy
- Know the signs and symptoms of preterm labor
If you’d like to learn more about staying healthy during pregnancy, you can read more on the National Institutes of Health website: https://www.nichd.nih.gov/health/topics/preconceptioncare/conditioninfo/healthy-pregnancy
How Can the PreTRM® Test Help Reduce Pregnancy Risk?
Doctors know of many medical and environmental risk factors that increase a woman’s risk of giving birth early.
However, many pregnancies still end in preterm labor, even when the mom has no known risk factors.
The PreTRM® Test for Risk Management is a simple blood test performed during weeks 18 through 20 of pregnancy. It measures the levels of proteins circulating in the blood that correspond with a higher than average risk of preterm labor. When you take the PreTRM Test, your doctor will get a report that shows your pregnancy’s risk of preterm birth so that you can prepare your support network.
With a risk report from your PreTRM Test, you and your doctor will be able to understand your risk of delivering early and adjust your prenatal care as needed. For more information about how the PreTRM Test process works, read PreTRM FAQs for Parents.
What is the earliest a baby can be born without complications?
Medical experts generally consider 37 weeks as the threshold for full-term pregnancy, which implies
that babies born after this period are less likely to face complications. However, some cases of
preterm births before 37 weeks may still result in favorable outcomes, as modern neonatal care and
medical advancements continue to improve.
Early detection of preterm labor signs is crucial to implement timely interventions. Prenatal care and
regular check-ups allow healthcare providers to monitor the mother and the baby’s well-being,
potentially mitigating the risk of preterm birth and its associated complications.
What are 3 warning signs of premature labor?
As an expectant mother, staying vigilant for any potential signs of preterm labor is crucial in ensuring
a healthy pregnancy and the best possible outcome for your baby. Preterm labor refers to labor that
starts before 37 weeks of gestation, putting both mother and baby at risk for complications.
Persistent Contractions: One of the primary warning signs of preterm labor is experiencing persistent
contractions that occur every 10 minutes or more frequently. These contractions may feel like a
tightening or cramping sensation in the abdomen and may not go away with rest or hydration.
Vaginal Bleeding: Vaginal bleeding that is more than just light spotting can be a red flag for preterm
labor. If you notice any bleeding, regardless of the amount, it’s essential to contact your healthcare
Change in Vaginal Discharge: A sudden increase in vaginal discharge, especially if it becomes watery
or contains mucus, can indicate the onset of preterm labor.
If you experience any of these warning signs, it’s crucial to seek medical attention promptly. Early
detection and intervention can make a significant difference in preventing preterm birth and its
potential complications. Your healthcare provider will assess your symptoms, conduct necessary
tests, and may recommend measures to delay labor or provide specialized care to support the baby’s
When is a premature baby out of danger?
The timeline for a premature baby to be out of danger varies depending on several factors, including
the baby’s gestational age at birth, overall health, and access to specialized neonatal care. Generally,
the closer a premature baby is to full-term (37 weeks), the less likely they are to face severe
In the initial days and weeks after birth, preterm infants are carefully monitored in a neonatal
intensive care unit (NICU) by a team of experienced medical professionals. This specialized care
aims to support their respiratory, nutritional, and developmental needs.
Many preterm babies achieve important developmental milestones and gradually outgrow the most
critical phase of vulnerability with the help of medical interventions. However, each baby is unique,
and the journey to being out of danger may differ for every preterm infant.
Talk to your doctor today about the PreTRM Test for your individual risk assessment.