None — Prematurity
A normal pregnancy lasts about 40 weeks. Prematurity is the birth of a baby before 37 weeks of gestation. When a baby is born too early, he/she hasn't had enough time to fully develop. Many premature infants can't eat on their own or regulate their body temperature. Preemies are also at high risk for a number of complications, like respiratory distress syndrome, congenital heart problems, retinopathy (a type of vision loss), hearing problems, infections, brain bleeding, cerebral palsy and learning or developmental disabilities. Most babies require a longer hospital stay and many need specialized care in the neonatal intensive care unit (NICU).
The March of Dimes reports about one in eight babies in the U.S. is born prematurely. In 2006, there were nearly 543,000 preterm births in this country. The CDC estimates the first year medical cost for the care of a preterm baby is about ten times that for a full term baby.
Charting Preemie Growth
Infants in the NICU are monitored continually to detect early signs of complications and ensure the babies are growing appropriately. Growth is measured and plotted on a standardized chart comparing average growth rates of other babies. One group of standardized growth charts is the Lubchenco curves. These charts were developed based on measurements of weight, length and head circumference from about 5,000 white infants from the Denver area between the 1940s and 1960s. Irene E. Olsen, Ph.D., R.D., Researcher with the University of Pennsylvania School of Nursing in Philadelphia, PA, says though these charts are still in use today, they are outdated and don't reflect growth curves of babies from various socioeconomic and ethnic backgrounds. Some new growth charts have been developed, but these only provide information on weight for age, not length or head circumference, two very important measurements for preemies.
Olsen and her colleagues pooled information from the database of the Pediatrix Medical Group. This database contains the records of more than 391,000 newborns (22 to 42 weeks) from 248 hospitals in 33 states who were born between 1998 and 2006. The measurements included birth weight, length, head circumference, estimated gestational age, gender and race.
Once the raw data was gathered, the researchers fit the information onto charts to reflect average growth curves. The curves were then validated. The investigators found wide enough variations between the sexes to develop three charts for boys and three for girls.
The researchers then compared the use of the new growth curves against the Lubchenco curves and found the new curves differed greatly from the standard charts at both the upper and lower range of gestational age. In general, the new growth curves reflected a lower weight, length and head circumference for very premature babies and a higher weight, length and head circumference for babies closer to full-term.
Olsen says the new growth curves show that some preemies may have been misclassified and doctors may be missing opportunities to provide the best care. For example, preemies who fall in the lower ranges of the growth curve may need extra nutritional support to grow. On the other hand, those in the upper ranges may be producing too much insulin and may be at risk for hypoglycemia.
The new growth curves were published in the February 2010 issue of the journal, Pediatrics. Olsen hopes the charts may one day be used by physicians around the country to track the growth of both preterm and full term babies.
For general information on prematurity:
American Academy of Pediatrics Centers for Disease Control and Prevention March of Dimes National Institute of Child Health and Human Development
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