Figure 2 summarises the numbers of participants
approached, consented and included in the analysis. The
median time from the first vaginal examination at full
dilatation to the time of the ultrasound was 15 minutes,
and the interquartile range was 12 minutes. Of these, 19
were OP, 141 were OA and 39 were OT, giving a relative
rate of the OP position less than expected.4 There were no
differences in maternal demographics between the OP and
OA groups (Table 1).
The OP and OA groups had similar clinical
characteristics including parity, gestational hypertension or
diabetes, induction of labour and epidural anaesthesia in
labour (Table 1). Only one woman had had a previous
caesarean section. Her fetus was in the OA position early
in the second stage of labour, and she had a normal
vaginal birth.
In the univariate analysis, the overall operative delivery
rate in the OP group was 68% compared with 27% in the
OA group (v2 = 12.7, P < 0.001) (Table 2). The
caesarean section rate was 37% in the OP group versus