National Women's Annual Clinical Report 2010

Table 40: Gestation at birth among women whose primary indication for induction was ‘post dates’
Gestation at birth
Total
n=362
Age 35
n=102
n % n % n %
39
5 1.4 2 0.8 3 2.9
40 – 40 6
35 9.7 18 6.9 17 16.7
41 – 41 6
245 67.7 177 68.1 68 66.7
42 – 42 6
74 20.4 61 23.5 13 12.8
43 3 0.8 2 0.8 1 1.0
Post dates pregnancy and term PROM were the most common primary reasons given for
induction of labour in 2010, similar to 2009.
When post-dates was the primary indication for induction, 11% occurred prior to 41 weeks
and 21% occurred at or beyond 42 weeks.
Mode of birth following induced and spontaneous onset of labour by parity
100
90
80
70
60
50
40
30
20
10
0
% Spontaneous vaginal birth Instrumental vaginal CS emergency
Nullipara
spontaneous labour
Nullipara induced
labour
Multipara
spontaneous labour
Multipara induced
labour
Figure 50: Mode of birth among intended vaginal births at term by parity and onset of labour
(excludes previous Caesarean)
The emergency Caesarean section rate following induction is higher than following
spontaneous onset of labour, for both nullipara and multipara without previous Caesarean.
Among nulliparous women, induction is associated with a 2-fold increase in risk of
emergency caesarean (from 15% to over 30%). While induction may contribute to this, some
of the difference is due to the indication for induction.
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