• Victoria M Allen, Thomas F Baskett, and Colleen M O'Connell.
• Department of Obstetrics and Gynaecology, Dalhousie University, Halifax, NS.
• J Obstet Gynaecol Can. 2010 Jul 1; 32 (7): 633-41.

ObjectiveTo estimate the contribution of select maternal groups to temporal trends in Caesarean section (CS) rates.MethodsUsing the Nova Scotia Atlee Perinatal Database, all deliveries by CS during the 24-year period from 1984 to 2007, at the Women's Hospital, IWK Health Centre were identified. Deliveries by CS were classified into groups using parity (nullipara/multipara), plurality (singleton/multiple), presentation (cephalic/breech/transverse), gestational age (term/preterm), history of previous CS (previous CS/no previous CS), and labour (spontaneous/induced/no labour). CS rates in each group and the contribution of each group to the overall CS rate was determined for three eight-year epochs. The risk of CS in each group over time, accounting for identified maternal, fetal, and obstetric practice factors, was evaluated using logistic regression.ResultsOf 113,016 deliveries, 23,232 (20.6%) were identified as deliveries by CS meeting the inclusion and exclusion criteria. The CS rate rose from 16.8% in 1984 to 1991 to 26.8% in 2000 to 2007 (P < 0.001). The biggest contributors to the overall CS rate in the last study epoch (2000-2007) were nulliparous women with singleton, cephalic, term pregnancies with spontaneous or induced labour; women with singleton, cephalic, term pregnancies with previous CS; and women with breech presentation. Adjusted analyses explained some increases in the rate of CS and demonstrated reduced risks in others.ConclusionOnly some temporally increased CS rates in select maternal groups remain increased after adjusting for confounding variables. The identification of potentially modifiable maternal risk factors, re-evaluation of the indications and techniques for induction of labour in nulliparous women, provision of clinical services for vaginal birth after Caesarean section, and external cephalic version for selected breech presentation are important clinical management areas to consider for safely lowering the Caesarean section rate.

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