Premature Birth Is the Leading Cause of Death Among Infants in the U.S.

Premature delivery — birth before 37 full weeks of gestation — is the leading cause of death among infants in the U.S. Babies who survive a preterm birth remain vulnerable to a host of health complications. The earlier the baby is born, the higher the risk. Very preterm babies (born before 32 weeks) are at increased risk for cerebral palsy, mental retardation, hearing loss and vision impairment. As they grow older, they are more prone than full-term babies to learning difficulties, behavioral disorders and emotional problems.2

Even lower-risk preterm babies—those born only a few weeks early—are more likely than full-term babies to develop hypoglycemia, respiratory distress and brain abnormalities. They also score lower, on average, on measures of intellectual ability, language comprehension, and memory.3,4

Prematurity and low birth weight are closely connected.

Prematurity is usually measured by gestational age (the length of time a newborn has spent in the womb). Because determining gestational age is often difficult, birth weight is frequently used as a substitute. All babies born at less than 5 lbs. 8 oz. are considered low birth weight; however, health risks can vary widely among this group. The lower the weight, the higher the baby’s risk.

  • Babies born at less than 3 lbs. 5 oz. (very low birth weight) have an infant mortality rate 77 times higher than normal-weight babies. Those who survive remain vulnerable to brain damage or abnormal brain development.5 Almost all very low birth-weight babies are born prematurely.
  • Newborns weighing less than 2 lbs. 3 oz. (extremely low birth weight) have a survival rate of about 60 percent. Babies who survive are at risk for cerebral palsy, severe cognitive delay, and other severe impairments. Those who manage to escape major impairments are still at risk for changes in brain function that may not emerge until young adulthood.6,7
  • Even babies whose weights are only moderately low (between 3 lbs. 5 oz. and 5 lbs. 8 oz.) have worse outcomes than normal birth-weight babies, even after maternal background differences are accounted for. They have, on average, higher mortality, poorer health, and more learning disabilities.8
  1. Callaghan WM, MacDorman MF, Rasmussen SA, et al. The Contribution of Preterm Birth to Infant Mortality Rates in the United States. Pediatrics. 2006; 118:1566-1573.
  2. Cheong JLY, Hunt RW, Anderson PJ, et al. Head growth in preterm infants: correlation with magnetic resonance imaging and neurodevelopmental outcome. Pediatrics. 2008; 121: e1534-e1540.
  3. Caravale B, Tozzi C, Albino G, et al. Cognitive development in low risk preterm infants at 3–4 years of life. Archives of Disease in Childhood Fetal and Neonatal Edition. 2005; 90: F474-F479.
  4. Peterson BS, Anderson AW, Ehrenkranz R, et al. Regional brain volumes and their later neurodevelopmental correlates in term and preterm infants. Pediatrics. 2003; 111: 939-948.
  5. Conrad AL, Richman L, Lindgren S, et al. Biological and environmental predictors of behavioral sequelae in children born preterm. Pediatrics. 2010; 125(1): e83–e89.
  6. Bassler D, Stoll BJ, Schmidt B, et al. Using a Count of Neonatal Morbidities to Predict Poor Outcome in Extremely Low Birth Weight Infants: Added Role of Neonatal Infection. Pediatrics. 2009; 123(1): 313-318.
  7. Schmidt LA, Miskovic V, Boyle M et al. Frontal Electroencephalogram Asymmetry, Salivary Cortisol, and Internalizing Behavior Problems in Young Adults Who Were Born at Extremely Low Birth Weight. Child Development. 2010; 81(1): 183–199.
  8. Stein REK, Siegel MJ, Bauman LJ, et al. Are Children of Moderately Low Birth Weight at Increased Risk for Poor Health? A New Look at an Old Question. Pediatrics. 2006; 118: 217-223.