BUFFALO, N.Y. – Babies considered
“early-term,” born at 37 or 38 weeks after a
mother’s last menstrual period, may look as healthy as
full-term babies born at 39-41 weeks, but a study published
yesterday by University at Buffalo physicians in JAMA Pediatrics
has found that many of them are not.
The study is considered the first population-based, countywide
assessment of neonatal morbidity among early-term infants based on
individual medical records in the U.S.
“Our results show the need for an increased awareness
among health care providers that even though we consider babies
born at 37 or 38 weeks almost term, they are still, to a large
extent, physiologically immature,” says Shaon Sengupta, MD,
corresponding author and formerly a UB medical resident in the
Department of Pediatrics and Women and Children’s Hospital of
Buffalo. She is currently doing a neonatal-perinatal medicine
fellowship at Children’s Hospital of Philadelphia.
The UB researchers found that these early-term babies were at
significantly higher risk for adverse outcomes. They also found
that birth by elective cesarean section pushed those risks even
higher, from 9.7 percent risk of admission to neonatal intensive
care with vaginal deliveries to 19 percent following cesarean
The research covered nearly 30,000 live births in Erie County
(which includes the city of Buffalo) from Jan. 1, 2006 through Dec.
In an accompanying editorial, William Oh of Brown University and
Tonse N. K. Raju of the Eunice Kennedy Shriver National Institute
of Child Health and Human Development, said that the findings
“…have important implications for obstetric and
neonatal care and research. The findings reinforce the concept that
maturation is a continuum and any preset gestational age cannot be
assumed to provide a clear separation between immaturity and
The study was precipitated by observations among neonatologists
that babies born at 37 or 38 weeks had more adverse health outcomes
than those born at 39 to 41 weeks,
according to Satyan Lakshminrusimha, MD, senior author on the
study, associate professor of pediatrics in the UB School of
Medicine and Biomedical Sciences and chief, division of neonatology
at Women and Children's Hospital of Buffalo. He has worked in the
hospital’s Neonatal Intensive Care Unit (NICU) since
“We were seeing a significant number of infants born at 37
weeks who looked big and pretty healthy, but who, within a few
hours of birth were developing low blood sugar, difficulty in
breathing or needed antibiotics, necessitating admission to the
neonatal intensive care unit,” says Lakshminrusimha.
After evaluating admission patterns among newborn infants
between 37 and 41 weeks of gestation at Women and Children’s
Hospital, Lakshminrusimha, Sengupta and colleagues found that these
early-term infants were more likely to suffer some morbidity within
a few hours of birth.
To see if these patterns were valid in a wider population, they
undertook the larger, county-wide study, conducting an analysis of
births at Women and Children’s, Millard Fillmore Suburban,
Sisters of Charity Hospital and Mercy Hospital, located either in
the city of Buffalo or its nearby suburbs.
These data showed similar patterns. Adverse outcomes experienced
by the early term babies included hypoglycemia (4.9 percent versus
2.5 percent of full-term babies), admission to the neonatal
intensive care unit (8.8 percent versus 5.3 percent, the need for
respiratory support (2.0 percent versus 1.1 percent), the need for
intravenous fluids (7.5 percent versus 4.4 percent) intravenous
antibiotics (2.6 percent versus 1.6 percent) and mechanical
ventilation or intubation, which was required in .6 percent of
early term babies versus .1 percent in full-term babies.
“Although these early-term babies appeared to be mature,
providing a false assurance to clinical providers and parents, and
they did well on the Apgar scores, they are nevertheless
physiologically immature,” notes Lakshminrusimha.
The data revealed, for example, that twice as many of these
early term babies needed mechanical ventilation and the need for
lung surfactant use was seven times higher than in term babies.
The data also show that early term babies delivered by cesarean
section were at a higher risk – by 12.2 percent -- for
admission to the NICU compared with full-term babies and at 7.5
percent higher risk for morbidity compared with term births.
In particular, the study points out that cesarean delivery is a
strong predictor of neonatal morbidity at early-term gestation.
Lakshminrusimha notes that the need for respiratory support is
increased for babies delivered by cesarean section who may retain
their fetal lung fluid, since they do not experience the hormonal
changes of labor, which clear the fluid from the lungs.
Sengupta launched the study as a UB medical resident in
pediatrics under Lakshminrusimha’s mentorship. While small
research projects are typically undertaken by medical residents,
Sengupta was capable of a larger study due to her motivation,
Lakshminrusimha says, and because she came to the UB residency
program with a Master’s in Public Health from Johns Hopkins
Additional co-authors are: Vivien Carrion, MD, associate
professor of pediatrics at UB and director of the Neonatal
Transport Team at Women and Children’s Hospital of Buffalo;
James Shelton, clinical assistant professor in the UB Department of
Gynecology and Obstetrics; Ralph J. Wynn, MD, associate professor
of pediatrics at UB; Rita M. Ryan, MD, formerly professor of
pediatrics at UB (currently chair of pediatrics at Medical
University of South Carolina) and Kamal Singhal, MD, neonatologist
at Sisters of Charity Hospital.
The research was funded by UB’s Division of Neonatology,
UB’s Thomas F. Frawley MD Residency Research Fellowship Fund
and an American Academy of Pediatrics Resident Research Grant.