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Maternal–Fetal Medicine
Prevention of Pre-term Birth—A Challenge Not Yet Met
a report by
Michele Kiely, DrPH
Chief, Collaborative Studies Unit, Eunice Kennedy Shriver National Institute of Child Health and Human Development
Pre-term birth is a serious, common, and costly public health problem that, history of previous pre-term birth, a history of premature rupture of the
despite much effort, remains one of the most complicated and difficult membranes, a history of cervical surgery, having the pregnancy conceived by
problems to address. Pre-term births are those that occur before 37 complete artificial reproductive technology, uterine anomalies, short cervical length,
weeks of gestation and are divided into two categories: ‘very pre-term’ (less chronic maternal health problems (hypertension, diabetes, urinary tract
than 32 weeks’ gestation) or ‘moderately pre-term’ (32–36 weeks’ infection), low pre-pregnancy maternal weight, stress, low socioeconomic
gestation). In 2006, pre-term births rose to 12.8% of all births. This
represents a 21% rise in pre-term births since 1990.
1
With the increasingly rapid rise in the
An infant born pre-term is at increased risk for both morbidity and mortality.
While survival rates for pre-term infants have improved in recent years, infants
rate of pre-term birth, the percentage of
born pre-term are at risk for developing a large number of complications.
infant deaths due to pre-term births has
Morbidity is inversely related to gestational age, but even late pre-term births
are at increased risk. In addition, the survival rates for very early pre-term
risen from 65.6% in 2000 to 68.6% of all
births have increased because of technological advances and the collaborative
infant deaths in 2005.
efforts of obstetricians and neonatologists. The list of newborn complications
is quite long. It includes, but is not limited to, temperature instability,
respiratory distress, apnea, hypoglycemia, seizures, jaundice, feeding status, cigarette smoking, illegal substance use, polyhydramnios, infections
difficulties, and rehospitalization. Premature babies are at increased risk for during pregnancy such as bacterial vaginosis and trichomoniasis, and having a
cerebral palsy, mental retardation, lung and gastrointestinal problems, and shortened cervix. However, many of the women who deliver pre-term have
vision and hearing loss.
2
In addition, pre-term birth is an important risk factor none of these risk factors. This brief review will focus on methods used to
for infant mortality. With the increasingly rapid rise in the rate of pre-term prevent pre-term delivery.
birth, the percentage of infant deaths due to pre-term births has risen from
65.6% in 2000 to 68.6% of all infant deaths in 2005.
3
Progesterone
Although not applicable to all populations, progesterone administration is
Multiple gestations carry a significant risk for pre-term delivery. The twin rate currently one of the few treatments available that appears to reduce the risk
increased from 1.8% between 1971 and 1977 to 2.8% in 1998
4
to 3.2% in for pre-term birth in some women. The most recent trials were by da Fonseca
2005.
5
The triplet and higher-order multiple birth rate increased from 0.03% in and colleagues,
7
Meis and colleagues for the Eunice Kennedy Shriver National
1971–1975 to 0.13% in 1995 to 0.16% in 2005.
5
Increases in triplet rates Institute of Child Health and Human Development Maternal-Fetal Medicine
were much more marked among births to university-educated women and Units Network (NICHD-MFMU),
8
including secondary analyses of the latter
women above 30 years of age.
4
Nearly 60% of twins and nearly all triplet study,
9–10
and Rouse and colleagues, also for the NICHD-MFMU.
11
In a small trial
and higher-order multiple births will be born pre-term.
6
In addition to multiple in Brazil, de Fonseca found that prophylactic administration of a vaginal
gestations, there is a long list of risk factors for pre-term delivery, including a progesterone suppository in high-risk women significantly reduced the
incidence of pre-term birth.
7
The study from the NICHD-MFMU also recruited
high-risk women. The treatment group received intramuscular injections of 17
Michele Kiely, DrPH, is Chief of the Collaborative Studies Unit at
alpha-hydroxyprogesterone. Women in the treatment group were significantly
the Eunice Kennedy Shriver National Institute of Child Health and
Human Development, where she runs the National Institutes of
less likely to deliver before 37 weeks (relative risk [RR] 0.66, 95% confidence
Health-District of Columbia Initiative to Reduce Infant Mortality interval [CI] 0.54–0.81), before 35 weeks (RR 0.67, 95% CI 0.48-0.93), and
in Minority Populations. She was previously a Senior Visiting
before 32 weeks (RR 0.58, 95% CI 0.37-0.91).
8
When the analyses were
Scientist in the Office of the Surgeon General, and edited
Reproductive and Perinatal Epidemiology. Between 2001 and
further refined by gestation at the time of the previous pre-term birth, women
2007 she was the American Co-Editor of Paediatric and Perinatal whose previous deliveries were at 20–27.9 and 28–33.9 weeks of pregnancy
Epidemiology. Dr Kiely is a Member of the Society for Pediatric
delivered at significantly later gestational ages when treated with
and Perinatal Epidemiology (SPER) and the American Public Health Association (APHA).
progesterone. Women whose previous delivery was between 34 and 36.9
E: kielym@nih.gov
weeks of pregnancy showed no benefit from treatment compared with
controls. Treatment with 17 alpha-hydroxyprogesterone did not reduce the rate
48 © TOUCH BRIEFINGS 2008
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