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Impaired contraction of the womb could be a contributor to the
association between older maternal age and the increased rate of
cesarean sections, according to a study released on June 30, 2008 in
the open access journal PLoS Medicine.
A cesarean section, sometimes also called a c-section, is a method of
childbirth in which the newborn is surgically removed from the uterus.
C-sections are associated with higher mortality and morbidity rates
than vaginal deliveries, and are thus often reserved for cases in which
vaginal birth could put the mother's or baby's life at risk. The rate
of cesarean section performance has increased considerably in the last
20 to 30 years in the developed world, which could have implications
for not just the mother and baby but also healthcare providers and
policy makers. According to the World Health Organization (WHO),
acceptable cesarean rates are between 10-15% in any given developed
countries. In light of this, they report the following rates: 20% in
the United Kingdom in 2004, 22.5% in Canada in 2001 and 2002, 30.2% in
the United States in 2005.
Earlier studies indicate that increased maternal age generally
increases the rate of cesarean performance, and this trend has been
shown in many different countries. However, the reason for this
association is unclear, and it is unknown to what extent this
association is true. These questions were tacked in a two part study
run by Professor Gordon Smith and colleagues at Cambridge University in
the United Kingdom.
In the first part of the study, a large set of data taken in Scotland,
known as theScottish Morbidity Record (SMR2) was used to
examine the association between maternal age and the outcome of labor.
The records, taken between 1980 and 2005, comprised half of a million
records. Specifically, they examined what proportion of the increase in
c-section rates could be directly associated with a change in maternal
age distribution. It was found that the risk of a cesarean section
increased linearly as the age of the expectant first time mother
increased. Over time, additional trends were observed in the proportion
of women in age group: the number of women between 30 and 34 years
increased three-fold, between 35 and 39 years increased seven-fold, and
over 40 doubled. IT was estimated that approximately 38% of these
additional cesarean surgeries could have been vaginal births if the age
distribution had remained constant after 1980. The team concluded from
this that a sizable portion of the cesarean section rate increase could
be due to delaying the first childbirth in a woman's life.
In the second part of the study, samples of muscle from the wall of the
uterus itself, known as myometrium, that were taken during the routine
surgery to examine the correlation between muscle contractility and
maternal age. The team hypothesized that it was this loss of the
ability of the muscle to contract, a biological effect of aging, was a
cause of the increased need for cesarean sections. The biopsies were
taken from 62 women, with a variety of number of previous births, who
were undergoing routine elective cesarean delivery. They found that
impaired uterine function was indeed associated with age as based on
the type of contraction and the ability of the muscle tissue to
contract.
In conjunction, the article states, these studies indicate that the
trend of advanced maternal age is not just associated with increased
cesarean sections, but that this substantial increase in cesareans
could potentially be caused by a decreased ability of the uterus to
function. Further work is necessary to determine if this causal
relationship is indeed true, but if explained, could help health care
professionals and policy makers make decisions that could reduce
population cesarean rates with minimal negative effects on maternal and
infant outcomes.
About PLoS Medicine
PLoS Medicine
is an open access, freely available international medical journal. It
publishes original research that enhances our understanding of human
health and disease, together with commentary and analysis of important
global health issues. For more information, visit http://www.plosmedicine.org.
About the Public Library of Science
The
Public Library of Science (PLoS) is a non-profit organization of
scientists and physicians committed to making the world's scientific
and medical literature a freely available public resource. For more
information, visit http://www.plos.org.
The effect of delaying childbirth on primary cesarean section
rates.
Smith GCS, Cordeaux Y, White IR, Pasupathy D, Missfelder-Lobos H, et al.
PLoS Med 5(7): e144.
doi:10.1371/journal.pmed.0050144.
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Written by Anna Sophia McKenney
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