Abstract
Objective To identify risk factors strongly associated with
failed mid-cavity vacuum-assisted delivery (VAD) and construct a risk
model that can be used to guide obstetricians in choosing between the
standard delivery room or the operating theatre. Design
Observational analytical predictive prospective monocentric study.
Setting University Hospital of Besançon, France, 2010-2018.
Population All successful (n=903) and failed (n=194) attempts
at mid-cavity VAD among term singleton deliveries. Methods
Bivariate and multivariate analyses with logistic regression were used
to determine the effects of 15 potential factors on the risk of VAD
failure. Main outcome measures Mode of delivery following an
attempt at mid-cavity VAD. Results The score comprised seven
variables significantly associated with failed mid-cavity VAD:
head-perineum distance ≥51 mm (p<0.001), bulky caput
succedaneum (p<0.001), maternal height ≤1.54 m
(p<0.001), duration of expulsive efforts before vacuum
<21 minutes or >30 minutes (p=0.0013), duration
from five centimetres to complete cervical dilation ≥3 hours (p=0.0091),
term ≥42 weeks of gestation (p=0.032), and occiput-posterior or
occiput-transverse fetal head position (p=0.041). The model was reliable
(Hosmer-Lemeshow test =8.5; p=0.39) and accurate (concordance index
=0.74). The threshold for a transfer to the operating theatre was set at
16.3 %. Advanced preparation of caesarean section equipment and
anticipated extension of epidural analgesia were significantly
associated with a decrease in the delay between VAD failure and birth by
caesarean section (p<0.001). Conclusions This model
could help obstetricians to better assess the risk of failed mid-cavity
VAD and to choose the appropriate place to perform it. Keywords
Vacuum-assisted delivery; mid-cavity.