Epidemiology of preterm birthBMJ 2004; 329 doi: https://doi.org/10.1136/bmj.329.7467.675 (Published 16 September 2004) Cite this as: BMJ 2004;329:675
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To the Editor:
We are delighted to see BMJ’s series "ABC of preterm birth", which
will certainly contribute to a better understanding and greater awareness
of the complex problem of prematurity, the leading obstetrical challenge.
However, there is growing evidence to contradict Tucker and McGuire’s
statement in the first article of the twelve part series, “The outcomes
for preterm infants born at or after 32 weeks of gestation are similar to
those for term infants (1).”
Data from 1989 to 1997 published by Demissie et al. in the American
Journal of Epidemiology demonstrated a linear relationship between
decreasing neonatal mortality and increasing gestational age based on
National Center for Health Statistics data linking livebirth and infant
death records. Neonatal mortality decreased with each week of gestation
gained and did not plateau at 32 or even 34 weeks (2). Most groups
continued to experience decreasing neonatal mortality through 36 weeks.
In 2002, Jones et al. studied infants with preterm birth at 34, 35,
or 36 weeks and found that, “Rates of NICU admission, respiratory distress
syndrome (RDS), ventilator use, and nursery related costs decreased
significantly with each week gained (3).”
Most recently, in 2004, Wang et al. published data from a case-
control study in Massachusetts indicating that, “Near-term infants had
significantly more medical problems and increased hospital costs compared
with contemporaneous full-term infants (4).” The study showed that babies
born between 35 and 36 6/7 weeks gestation experienced significantly more
temperature instability and respiratory distress, required more
intravenous infusions, and were clinically jaundiced more often than term
These studies of short-term outcomes suggest that each additional
week of gestation contributes to better birth outcomes.
Further studies are needed to evaluate long term outcomes for preterm
infants and to quantify the morbidity of prematurity. Such data will
provide valuable information for clinicians and families and allow them to
accurately weigh the risks and benefits of preterm delivery. In the
meantime, statements indicating that the outcomes of near term infants are
the same as term infants are not evidence-based and may be contributing to
preterm birth rates by underestimating the risk.
In January of 2003, the March of Dimes launched a five year, seventy-
five million dollar campaign to raise pubic awareness and stimulate
research into the serious problem of prematurity. March of Dimes therefore
joins BMJ in focusing educational and research efforts on the complex
problem of prematurity.
Siobhan M. Dolan, MD, MPH.
Associate Medical Director, March of Dimes and Assistant Professor,
Department of Obstetrics & Gynecology and Women’s Health,
Albert Einstein College of Medicine / Montefiore Medical Center.
Joann Petrini, PhD, MPH.
Director, Perinatal Data Center,
March of Dimes and Assistant Professor, Department of Obstetrics &
Gynecology and Women’s Health, Albert Einstein College of Medicine.
Karla Damus, RN, MSPH, PhD.
Senior Research Associate & Epidemiologist, March of Dimes and
Department of Obstetrics & Gynecology and Women’s Health, Albert
Einstein College of Medicine.
1. Tucker J, McGuire W. Epidemiology of preterm birth. BMJ
2. Demissie K, Rhoads GG, Ananth CV, Alexander GR, Kramer MS, Kogan MD, et
al. Trends in preterm birth and neonatal mortality among blacks and whites
in the United States from 1989 to 1997. Am J Epidemiol 2001;154(4):307-15.
3. Jones JS, Istwan NB, Jacques D, Coleman SK, Stanziano G. Is 34 weeks an
acceptable goal for a complicated singleton pregnancy? Manag Care
4. Wang ML, Dorer DJ, Fleming MP, Catlin EA. Clinical outcomes of near-
term infants. Pediatrics 2004;114(2):372-6.
Competing interests: No competing interests
Tucker and Mcguire point out that modern perinatal care and the
specific interventions of antenatal steroids and exogenous surfactant have
contributed to the improved outcomes for very preterm infants. As an
obstetric registrar in Ninewells Hospital in the mid 70’s I was taught and
practiced delayed cord clamping at delivery of the preterm infant. This
measure has since been shown to reduce the severity of respiratory
distress syndrome (1) and neonatal morbidity.(2)
Despite the evidence of benefit, timing of clamping the cord was not
included in the 27/28 week CESDI project as a standard of care. A recent
postal survey of obstetricians regularly delivering preterm infants showed
that only 47% practiced delayed cord clamping. Nor is this measure
specified by Tucker and Mcguire in their review article.
We agree that prevention of preterm birth, or the need for it,
provided by an adequate research based treatment, must be the ultimate
aim. When prevention is not possible every measure which reduces the
morbidity and mortality of the infant must be given. Currently this does
not appear to be the case in the UK.
1. Kimond S et al. Umbilical cord clamping and preterm infants: a
randomised controlled trial. BMJ (1993);306:172-5
2. Rabe H et al. A randomised controlled trial of delayed cord clamping in
very low birth weight preterm infants. Eur J Paediatr (2000);159(10):775-7
3. British Congress of Obstetrics and Gynaecology. (2004) Glasgow. What is
the contribution of delayed cord clamping during delivery of the preterm
bay to the reduction in morbidity and mortality of the neonate? DJR
Hutchon and MR Houda.
Competing interests: No competing interests