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The Problem with Late-Preterm Birth Fact Sheet

What is late-preterm birth?

Late-preterm birth happens when a baby is born between 34 and 36 weeks of gestation. This is more than a month too soon, and the baby's major organs have not had the normal amount of time to mature. It's helpful to know that a woman's due date is based on 40 full weeks of pregnancy. That means that at 36 weeks most babies still need another month to continue growing in order to enter the world with appropriately developed organs and systems. Because the baby is growing, the last month of pregnancy can be uncomfortable for the mother; she needs support to encourage her that a healthy baby is worth the wait.

Why Wait?

The baby's due date is only an estimate.
The due date for the baby is an estimated date and can be off by two weeks either way, even using ultrasound for setting the date. This means that a woman might be 38 weeks pregnant based on her estimated due date, only to discover at birth that her baby appears to be 36 weeks developed on exam. This is important because at 36 weeks the baby has not yet matured and may have more problems than if born at term, and some of the problems are very serious.

The baby's brain is underdeveloped.
The baby's brain is the last major organ to develop. At 35 weeks the baby's brain weighs only two-thirds of what it will weigh at full-term. The part of the brain we use for thinking, the cerebral cortex, almost doubles in size during those last few weeks. Huge numbers of connections between brain cells and different areas of the brain are being formed during that time. So it is very important that the baby remain in the protected environment of the womb while these changes are taking place (unless there are medical reasons that make it unsafe for the mother or the baby).

Late-preterm babies have more health problems.
Late-preterm babies, born between four and six weeks early, have a higher rate of many health problems than full-term babies. Compared to full-term babies,  late-preterm babies are more likely to have:

  • Breathing problems, which can be serious enough for the baby to need a ventilator.
  • Difficulty maintaining normal temperature.
  • Difficulty with blood sugar and feeding, with poor suck/swallow abilities.
  • Newborn jaundice, which can cause brain damage if it goes unusually high.
  • A longer hospital stay (or go home, only to be readmitted with problems later).
  • Smaller and less developed brains at the time of birth.
  • Higher rate of readmission to the hospital during infancy.
  • Increased risk for sudden infant death syndrome (SIDS).
  • Increased risk for ADHD, hyperactivity, behavior and learning problems.
  • Higher risk in adulthood for chronic diseases such as diabetes and heart disease.

Healthy Babies Are Worth the Wait® is a multifaceted partnership of the March of Dimes, the Johnson & Johnson Pediatric Institute and the Kentucky Department for Public Health. The primary goal of the initiative is a 15 percent reduction in the rate of "preventable" single preterm births - particularly babies born late-preterm (four to six weeks early) - in three targeted intervention sites in Kentucky: King's Daughters Medical Center in Ashland, Trover Health System Regional Medical Center of Hopkins County and the University of Kentucky Albert B. Chandler Hospital in Lexington. Health care teams at each site provide mothers-to-be with an integrated approach of education, counseling and clinical care.

For more information, call 1-800-333-8874 or visit our website or the following sites: 


Clinical outcomes of near-term infants, Pediatrics , vol. 114, pp. 372-376, 2004.

Optimizing care and outcome for late-preterm (near-term) infants: A summary of the workshop sponsored by the National Institute of Child Health and Human Development. Pediatrics, vol. 118, no. 3, pp. 1207-1214, 2006.

Short-term outcomes of infants born at 35 and 36 weeks gestation: We need to ask more questions. Seminars in Perinatology , vol. 30, pp. 28-33, 2006.

Neurodevelopmental outcome of the late preterm infant. Clinics in Perinatology, vol. 3, pp. 947-964, 2006.

Page last updated: 8/13/2014 4:26:12 PM