Gestational Age Not Sole Predictor of Preemie Survival
Four other factors, including gender and weight, play role in infant's chances, study finds
WEDNESDAY, April 16, 2008 (HealthDay News) -- When it comes to the survival of premature infants, the factor that doctors have traditionally focused on is gestational age, but a new study suggests that gestational age is just one of several factors that physicians and parents should consider when deciding what treatment, if any, is best.
The factors that can help physicians predict a very premature infant's chance of survival include gestational age, gender, birth weight, whether it's a single or multiple birth, and whether or not the mother took corticosteroids before the baby was born.
"Using these five factors in combination can really enhance judgment and inform physicians and parents," said study co-author Dr. Rosemary Higgins, a program scientist for the Neonatal Research Network, part of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) in Bethesda, Md.
But, she added, "Every child is an individual, and each decision needs to be made on a case-by-case basis. But this study reflects the overall experience for infants in our network and provides one more piece of information to use in determining the best course of action."
Determining the best course of action is often difficult when it comes to the most frail preterm infants. A normal pregnancy lasts 40 weeks. Babies born between 22 and 25 weeks' gestation have high mortality rates, and if they do survive, many have lifelong disabilities, such as hearing loss, blindness and cerebral palsy. Still, others survive and reach adulthood, seemingly unaffected by their early birth.
Some neonatal centers provide intensive care to every premature baby, no matter what their odds of survival are. Other centers may provide intensive care for 23- and 24-week-old preemies only with parental consent, and some only provide "comfort care" to babies born at 22 weeks' gestation, according to background information in the study, which was published in the April 17 issue of the New England Journal of Medicine.
However, gestational ages aren't always perfect -- they're usually the obstetrician's best estimate, according to the study.
To assess whether other factors were also important in predicting a premature infant's chances for survival, researchers from the University of Texas Medical School at Houston and from the NICHD prospectively studied a group of more than 4,000 premature infants born between 22 and 25 weeks' gestation. Eighty-three percent were given intensive care in the hospital.
At follow-up between 18 and 22 months later, 61 percent of the babies had either died or had profound impairment.
In those infants who received intensive care, four factors emerged as being somewhat protective, in addition to increased gestational age. Receiving corticosteroids before birth, being female, being a singleton birth, and being a higher birth weight (per each 100 gram increase in weight), were all associated with a reduction in the risk of death and disability similar to the reduction seen with a one week increase in gestational age.
The study authors use an example of a baby born between the 24th and 25th week of gestation. For a female who is the appropriate weight for her gestational age, is a singleton birth, and who received corticosteroids before birth, the risk of death or profound impairment is 33 percent. But for a male who's small for his gestation age, didn't receive corticosteroids and who's a twin, the risk of death or profound impairment jumps to 87 percent, according to the study.
"Traditional teaching is that viability is 24 weeks, but what they're saying is here are other factors that are important. It's highlighting something that we've already known, that there's not a sharp line. It's all much grayer than we thought," said Dr. Peter Bernstein, a maternal-fetal medicine specialist at Montefiore Medical Center in New York City.
But, he pointed out, "the outcomes are still pretty dismal" for these tiny babies.
However, he said this study will definitely be useful.
"Having these concrete numbers to go with is helpful. These numbers do a better job for us being able to counsel parents, and it helps with how much hope I might give the family," he said.
To learn more about who's at risk for preterm birth, visit the March of Dimes.