Overview of Late Preterm Infant Health

Newborn baby in incubator

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Late preterm infants are babies born between 34 and 37 weeks gestation. Late preterm infants don't necessarily appear premature—they often look like smaller versions of full-term babies.

For a long time, late preterm babies were treated like full-term babies. However, research has increasingly shown that these infants are not the same as full-term infants and that they have a unique set of needs and challenges.

Babies born close to term are considered preemies.​ Even after 37 weeks gestation, full-term infants may have some of the same problems as late preterm babies.

The risk of health problems related to prematurity starts to decline at around 37 weeks gestation but doesn't level off completely until 39 weeks.

What Are the Immediate Medical Risks?

In the hours after birth, babies face several challenges as they adjust to life outside the uterus. Breathing air, staying warm, and getting used to the world are all hard work!

Although many late preterm babies adjust just fine, some have trouble. Even late preterm babies born to healthy moms with no complications may face:

  • Respiratory problems. Respiratory problems occur in 4.2% of late preterm births, but only 0.1% of full-term births. Respiratory problems can be mild or severe and may include respiratory distress syndrome, transient tachypnea of the newborn, pulmonary hypertension, and the need for respiratory support.
  • Hypoglycemia. While only 0.4% of term babies suffer from low blood sugar in the hours after birth, 6.8% of late preterm babies are hypoglycemic after delivery. Babies who are born early have not stored as much sugar as full-term babies, which means they can easily become hypoglycemic when they are cold or stressed.
  • Poor thermoregulation. Preterm babies don't have as much stored fat as term babies, so they get cold easily. Cold babies burn more calories to try to stay warm, making hypoglycemia worse and slowing weight gain.

Concerns in the First Weeks

Late preterm babies still face challenges even after they make the initial adjustment to life outside the womb. Parents and pediatricians who care for late preterm babies need to make sure that these fragile infants stay healthy after they go home.

Health issues related to prematurity contribute to a high rate of hospital readmission in late preterm babies who are discharged within 48 hours of birth. These issues include:

  • Jaundice. Although only 2.5% of full-term babies have jaundice serious enough to need phototherapy, 18% of late preterm babies develop jaundice that requires treatment.
  • Feeding challenges. Late preterm babies get tired easily and may not be strong enough feeders to drink enough breast milk or formula to gain weight. This can cause dehydration or failure to thrive. Breastfeeding failure is another risk: moms whose infants do not breastfeed effectively may not produce enough milk to feed their babies.
  • Sepsis. A premature infant's immune system is not fully developed, which means they are at greater risk for infection than term babies. They are also more likely to have bloodwork drawn to test for infection and are more likely to require antibiotic therapy.

Further Concerns

Many of the issues that late preterm babies face are known to impact brain development. Unfortunately, most studies of long-term neurodevelopmental outcomes in premature babies have focused on babies born before 34 weeks.

What is known is that late preterm babies are at risk for developmental delay. More research is needed to track how late preterm babies go on to do in school as they grow older.

With all of this to consider, it's important for parents to remember is that with good care, the majority of late preterm infants are likely to do just fine.

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  • Darcy, A. MSN, RN. "Complications of the Late Preterm Infant." The Journal of Perinatal & Neonatal Nursing January/March 2009. 23;78-86.
  • Melamed, N. MD, Klinger, G. MD, Tenebaurm-Gavish, K. MD, Herscovici, T. MD, Linder, N., Hod, M. MD, Yogev, Y. MD. "Short-Term Neonatal Outcome in Low-Risk, Spontaneous, Singleton, Late Preterm Deliveries." Obstetrics & Gynecology August 2009. 114; 253-260.

By Cheryl Bird, RN, BSN
Cheryl Bird, RN, BSN, is a registered nurse in a tertiary level neonatal intensive care unit at Mary Washington Hospital in Fredericksburg, Virginia.