The risk of serious maternal morbidity progressively increases with the number of caesarean deliveries, according to a systematic review and meta-analysis of observational studies.
The rate of hysterectomy, blood transfusions, adhesions and surgical injury all increase with increasing number of caesarean deliveries, Dr Nicole E. Marshall and colleagues from the Oregon Health & Science University in Portland found.
They also found that women who have three or more caesarean sections have a significantly increased risk for placenta previa, placenta accreta and hysterectomy.
Still, the investigators emphasise that most women experience good outcomes, regardless of the number of prior caesareans, and therefore the data "do not suggest an upper limit to the number of allowable caesarean deliveries."
Nonetheless, they say women who plan to have several children should be counselled about the risks of multiple caesarean deliveries and the risks and benefits of vaginal birth after caesarean (VBAC) to help them make informed decisions.
Number of c-section births increasing
The research was presented at the annual meeting of the Society for Maternal-Fetal Medicine and published in the American Journal of Obstetrics and Gynecology.
In the United States, nearly a third of all births are by caesarean section, and the rate of both primary and repeat caesarean deliveries continues to trend upward each year. In the last 10 years, there has been a trend away from VBAC.
To determine the impact of increasing numbers of caesareans on maternal morbidity, Dr Marshall and colleagues systematically reviewed 21 studies that were selected using a "best evidence" approach, i.e., those with the highest quality and most rigorous design were emphasised.
The 21 studies included data on more than 2.2 million deliveries, including 180,177 repeat caesarean deliveries and 5,729 cases where a mother had at least three caesarean deliveries. There were 5,823 cases of placenta previa, 743 cases of accreta and 1,852 women required hysterectomy.
Cases came from a variety of countries, including the United States, Australia, the United Kingdom and Israel, and a variety of practise settings, including both academic and community-based health centres.
Caesarian births, hysterectomy numbers linked
Hysterectomy increased with increasing number of caesareans in all studies. The best evidence comes from a 2006 study that used the Eunice Kennedy Shriver Maternal-Fetal Medicine Units Network caesarean registry database. This study reported that as the number of caesareans went from one to five, the adjusted odds ratio for hysterectomy (compared to the risk in women with vaginal deliveries only) went from 0.7 to 1.4, 3.8, 5.6, and 15.2.
The primary indications for hysterectomy, listed in four studies, were placenta previa/accreta (67%), uterine atony (25%) and uterine rupture/laceration (5%).
The incidence of placenta previa per 1000 delivers rose from 10 with one prior caesarean to 28 with three or more prior caesareans, the authors report.
Compared to women without placenta previa and no prior caesarean delivery, women with placenta previa and three or more prior caesareans had a statistically significant increased risk of accreta (50% to 67% vs 3.3% to 4%), hysterectomy (50% to 67% vs 0.7% to 4%), and composite maternal morbidity (83% vs 15%).
"As the rate of caesarean deliveries continues to rise, hospitals and physicians need to be prepared to optimise management of women with multiple caesarean deliveries and minimise morbidity and mortality," the investigators conclude. - (Reuters Health, July 2011)
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