Infants are surviving outside the womb at younger gestational age and lower birth weight, but earlier preterm birth is associated with higher medical and nutritional risk. Preterm and low birth weight infants may require prolonged hospitalization for life support until they are of sufficient size, strength and maturity to be cared for at home.
Very low birth weight, VLBW, infants weigh less than 1,500 g or 3 lbs. and 5 oz.; extremely low birth weight, ELBW, infants weigh less than 1,000 g or 2 lbs. and 5 oz., according to Mary Mitchell in the book “Nutrition Across the Life Span.” Survival outside the womb at this stage of development requires intensive medical and nutritional care.
Advances in the technology available in infant intensive care units in recent decades have enabled smaller and smaller infants to survive. At the same time, a rising incidence of low birth weight in the United States is attributed to the rise in rates of multiple births associated with assisted reproduction technologies, according to Mitchell's book. As technology continues to advance the frontier of early birth survival, smaller and younger gestational age infants are able to thrive with the help of a team of health care professionals.
In the August 23, 2010 issue of “Pediatrics,” Dr. Barbara J. Stoll and colleagues present recent data on morbidity and mortality rates according to gestational age. Their analysis of data collected for more than 9,000 infants of extremely low birth weight and extremely low gestational age between 2003 and 2007 indicated that survival to discharge increased as gestational age increased, from 6 percent at 22 weeks to 92 percent at 28 weeks. The majority of infants of 24 weeks or greater survive, but high rates of morbidity are observed.
Very preterm infants have limited nutrient reserves because most nutrient transfer and fetal weight gain would have occurred in the third trimester of pregnancy. Tiny infants have inadequate fat stores to regulate their body temperature and need to be kept in incubators.
Inadequate nutrient stores and rapid growth rates pose challenges to the medical team in providing appropriate high mineral formulas, supplements or intravenous nutrition. For instance, a 1,500 g infant’s immature digestive tract and immature, uncoordinated sucking and swallowing, as well as a stomach capacity of only 3 ml at birth, limits the ability to provide adequate nutrition by mouth. In addition, Immature organs may not be able to regulate their own fluid, electrolyte and glucose levels, according to Mitchell in “Nutrition Across the Life Span.”
Preterm birth is associated with increased morbidity and mortality, according to Mitchell. For this reason, preterm and low birth weight infants are considered "high risk." Medical complications and surgical stresses may complicate the high-risk infant’s care. The hospital nutrition team for high-risk infants includes physicians, nurses, dietitians, pharmacists, developmental therapists and lactation specialists working together to provide optimal health care and the best opportunity for high-risk infants to thrive.
- “Nutrition Across the Life Span”; Mary Kay Mitchell; (2003)
- Pediatrics: Neonatal Outcomes of Extremely Preterm Infants From the NICHD Neonatal Research Network