Interpretation
The simple hierarchical classification system used in the study (Figure
1, Supplement 1) classifies intrapartum CS by the condition of the
fetus, rate of progress during labour and the use of oxytocin in an
inclusive and mutually exclusive manner.10, 12 This is
in contrast to a systematic review of indication-based classifications9 which identified only two out of twelve studies
using a mutually exclusive system 14, 15. Generally,
this review found low reproducibility in classification (disagreement in
45% of the cases [range 8%-83%]). The studies utilizing a
mutually exclusive classification 14, 15 incorporated
some elements of the TGCS into their indication system (previous CS and
breech), but did not differentiate between suspected fetal distress
according to use or non-use of oxytocin and whether the suspected fetal
distress was a primary factor or only occurred as a result of treatment
of dystocia. Both types of suspected fetal distress were accounted for
appropriately in the current study.
Detailed indications for intrapartum CS in Norway have been previously
reported based on the mandatory data collection in the Medical Birth
Registry of Norway.16-18 Interestingly an analysis of
the period 1967-84, classified 31 indications into seven high level
groups (mechanical, uterine, presentation, asphyxia, other fetal,
maternal, acute placental). More than one category though was present in
35% of all CS.16
A comparison of Scotland, Sweden, USA and Norway during the time period
1980-90, chose the first relevant in a hierarchy of five indications
(previous CS, breech presentation, dystocia, fetal distress, or other)
as the primary indication and were classified accordingly. The number of
CS with multiple indications was not reported. 17
A nationwide study in 1998-99 reported indications for CS using a
pre-determined set of 31 indications with up to four choices per case.18 In all three studies the classification systems
were also totally inclusive, but not mutually exclusive. Both the
arbitrary hierarchy 17 and the subjectivity related to
combinations among a set of indications 16, 18 make a
comparison impossible. Moreover, there was no division of CS into those
performed before and during labour and features characterizing women
according to the TGCS (breech presentation, previous CS) were partly
mixed with indications. 16-18
A Slovenian study applied a modified version of the ICSCS used in the
current study on deliveries in the TGCS group 1. 19They found intrapartum CS classified as Dystocia-Efficient uterine
action - CPD to be more prevalent as compared to Norway (3.1% vs.
0.2%). 19 Different clinical approaches to vaginal
operative delivery could explain this: instrumental delivery was
performed four times more frequently in Norway compared to
Slovenia.20
In a Swedish registry-based study on women in TGCS Group 1 and 2a for
the period 1999-2010 multiple indications accounted for 14% of all
intrapartum CS and an indication was missing in as many as 18% of
deliveries. 21
Other studies, based on either national or multicenter data did not
apply indications within the TGCS and their subgroups,22, 23 making it impossible to differentiate
pre-labour CS from those performed intrapartum. Multiple indications per
CS were also common and while they might provide a more complete
explanation of the clinical situation, they are not useful for
classification, comparison and learning from each other.