|NIH Study Reveals Factors That Influence Premature
Infant Survival, Disability
Based on observations of more than 4,000 infants, researchers
in an NIH newborn research network have identified several factors
that influence an extremely low birth weight infant's chances for
survival and disability. The findings offer new information to
physicians and families considering the most appropriate treatment
options for this category of infants.
Every day, physicians and new parents must struggle with the type
of care to provide to extremely low birth weight infants, the smallest,
most frail category of preterm infants. These infants are born
in the 22nd through the 25th week of pregnancy — far
earlier than the 40 weeks of a full term pregnancy. Many die soon
after birth, despite the best attempts to save them, including
the most sophisticated newborn intensive care available. Some survive
and reach adulthood, relatively unaffected. The rest will experience
some degree of life long disability, ranging from minor hearing
loss to blindness, to cerebral palsy, to profound intellectual
The study authors referred to the issue of providing intensive
care for extremely low birth weight infants. For example, physicians
and family members may be reluctant to expose an infant to painful
life support procedures if the infant is unlikely to survive. In
such cases, they may opt for "comfort care," which provides
for an infant's basic needs, but foregoes painful medical procedures.
In deciding the kind of care to provide, specialists at intensive
care facilities traditionally have relied heavily on an infant's
gestational age — the week of pregnancy a premature infant
is born. Gestational age is known to play a large role in the infant's
survival. For this reason, in many facilities, intensive care is
likely to be routinely given to infants born in the 25th week
of pregnancy, whereas infants born in the 22nd week
may be more likely to receive comfort care.
The study authors noted, however, that it is often difficult to
assess gestational age. Moreover, an estimate that is inaccurate
by only a week could result in an infant receiving care that was
not appropriate for his or her individual case. To identify other
factors that influenced survival and disability risk, the study
authors observed more than 4,000 extremely low birth weight infants
in their network.
The researchers published their findings in the April 17 New
England Journal of Medicine. In addition to gestational
age, factors influencing survival and risk of disability consisted
of: whether the baby is male or female (sex); birthweight; whether
the baby was a single baby, or one of two or more infants born;
and whether the baby's mother was given medication during pregnancy
to prompt the development of the baby's lungs. Known as antenatal
steroids, these drugs are typically given to women in premature
labor, or who are at known risk for giving birth prematurely.
Physicians and parents may access an online tool that generates
statistics, based on the factors the researchers listed in their
article, at http://www.nichd.nih.gov/about/org/cdbpm/pp/prog_epbo/.
By specifying the baby's sex, weight, and information related to
each of the variables listed above, physicians and family members
can generate composite statistics on infant outcomes, based on
the experiences of extremely low birthweight infants in the NICHD
Neonatal Research Network study. The Web tool is not a substitute
for a physician's careful assessment, but physicians and families
may find the statistics it generates useful when considering the
most appropriate care to provide an infant.
"Every individual is different, and no single tool can precisely
predict a given baby's chances of survival or disability," said
Duane Alexander, M.D., director of the Eunice Kennedy Shriver National
Institute of Child Health and Human Development (NICHD), the NIH
Institute that supports the Neonatal Research Network. "However,
the researchers' findings, and the tool they developed, provide
important information that physicians and family members can consult
to help them make the most informed treatment decisions possible."
Additional funding for the study was provided by NIH's National
Center for Research Resources.
The researchers were led by Jon E. Tyson, M.D., of the University
of Texas Medical School at Houston. Other authors of the study
were Nehal A. Parikh, D.O., and Charles Green, Ph.D., also of the
University of Texas Medical School at Houston; John Langer, M.S.,
of the Research Triangle Institute, Research Triangle Park, NC,
and Rosemary Higgins, M.D., the program scientist for the NICHD
Neonatal Research Network.
The study involved only infants born at level III neonatal intensive
care facilities. For this reason, the study findings may not apply
to infants born at level I and level II facilities.
Level III facilities are the most advanced of neonatal care facilities.
They offer the highly specialized medical care that extremely low
birth weight infants need to survive. Most extremely low birth
weight infants are born in level III facilities, as it is routine
practice to rush women likely to give birth prematurely to level
III facilities. However, in some cases, a woman may give birth
before she can be brought to a level III facility. These infants
are typically cared for at level I and II facilities until they
are stable enough to transport to a level III facility.
To conduct their analysis, researchers in the NICHD Neonatal Research
Network observed 4,446 infants born at 22-25 weeks' gestational
age at hospitals around the United States, explained the NICHD
co-author of the study, Rosemary Higgins, M.D.. Dr. Higgins said
that extremely low birthweight infants (those weighing less than
1,000 grams, or 2.2 pounds) make up about 1 percent of babies born
in the United States each year, or roughly 40,000 babies a year.
Using standardized measures of mental development, vision, and
hearing, the researchers assessed the health status of surviving
infants when the infants were from 18 to 22 months corrected age — the
age they would have been, had they been born full term. Dr. Higgins
said that 49 percent of the infants in the study had died, 21 percent
lived and did not have a disability, while the remainder experienced
some degree of disability.
After conducting mathematical analyses of all the infants' cases,
the researchers determined that infants were more likely to survive — and
more likely to survive without disability — if they were
of older gestational age, their mothers had been given corticosteroids,
if they were female, were single born rather than part of a multiple
birth, and been of a higher birthweight.
"Many neonatal intensive care units base treatment decisions
mainly on gestational age," said Dr. Higgins. "We found
that it's much more accurate if the assessment is based on the
combination of 5 factors, rather than just on gestational age."
Dr. Higgins added that it is often difficult to accurately estimate
gestational age, and a preterm infant may be as much as a week
or two younger, or older, than believed.
She noted that the researchers found that race appeared to play
no role in subsequent survival or chances of disability.
She stressed that the study data could not be used to predict
with certainty the outcome of individual cases.
"A lot of medicine is a judgment call," Dr. Higgins
said. "We provided our data in the hope that it would be helpful
for making the best judgments for a particular situation."
A video interview with Dr. Higgins in which she provides additional
information about the study and the online tool is available at http://www.nichd.nih.gov/news/resources/links/neonatal/.
The NICHD sponsors research on development, before and after birth;
maternal, child, and family health; reproductive biology and population
issues; and medical rehabilitation. For more information, visit
the Institute's Web site at http://www.nichd.nih.gov/.
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and
Centers and is a component of the U.S. Department of Health and
Human Services. It is the primary federal agency for conducting
and supporting basic, clinical and translational medical research,
and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and
its programs, visit www.nih.gov.