Strengths and Limitations
The following are considered limitations of this study. Large clinical
databases may be susceptible to data entry errors, however we have
demonstrated the accuracy of a portion (2005 to 2009) of this database
in the past.17 Some of the fields used in the analysis
were derived from multiple other fields, including some which allowed
free text entry. This could lead to misclassification of items such as
the indication for caesarean delivery or history of previous caesarean
delivery which could bias the findings in any direction. Missing data
(most commonly for maternal BMI) can lead to bias, but we used multiple
imputation to reduce this risk.
As the data were sourced from
only two institutions in one city our findings may not be generalizable
to other settings. Lack of information about the number of previous
caesarean deliveries could have led to underestimation of the proportion
of caesarean deliveries explained by maternal factors.
We believe this study had several strengths including the use of a large
dataset with near complete data for factors such as maternal age and
mode of birth which reduces information bias and the use of multiple
imputation to control for missing data. Unlike national databases, our
institutional database contained sufficient data fields to allow us to
subdivide our outcome into indications for caesarean delivery and Robson
categories.
Research is needed into the best way to manage labour as demographic
profiles of populations change. For example, it is not known if older
women or those with higher BMI require longer labours. There is evidence
that strategies such as induction of labour in selected
women18–22 or ceasing oxytocin in active
labour23 can increase vaginal birth rates. The
possibility that younger women are more susceptible to caesarean
delivery for fetal concerns due to uterine hyperstimulation could lead
to exploring intrapartum management options based on maternal
age.24 Studies are needed to establish the real value
of planned caesarean delivery for previous obstetric anal sphincter
injury or fetal concerns identified on antenatal ultrasound.