Data collection
Data were collected prospectively. For each woman included, we collected
data on the following: the final mode of delivery (success or failure of
the vacuum attempt), the values of the fifteen potential risk factors
previously described, the type of room where the VAD was attempted, the
neonatal outcomes (five-minute Apgar score, arterial umbilical cord
blood pH, immediate neonatal resuscitation, neonatal transfer location),
the maternal outcomes (perineal trauma, quantity of blood loss) and
whether the preparation of the C-section equipment had been anticipated.
In cases of C-section, we also collected data on whether the extension
of epidural anaesthesia had been anticipated, whether general
anaesthesia had been required, and the durations between the C-section
decision, skin incision and birth.
Fundal height was measured by the midwife at admission to the labour
room (regardless of a potential rupture of membranes). Cervical dilation
was evaluated by the midwife by digital vaginal examination every hour
during labour. The fetal head position at the beginning of the VAD was
evaluated by digital vaginal examination and transabdominal ultrasound.
The fetal head station at the beginning of the VAD was evaluated by the
head-perineum distance measured by trans-perineal ultrasound, according
to the method described by D. Maticot-Baptista et al. and the IUSOG:
outside of uterine contraction and without compression of the soft
tissue against the pubic bone 20,21. The presence of a
caput succedaneum was subjectively evaluated by the obstetrician by
digital vaginal examination and trans-perineal ultrasound, with three
possible outcomes: absent or insignificant/medium sized/bulky. The
perineal trauma was evaluated by the obstetrician according to the RCOG
classification of perineal tears. Immediate neonatal resuscitation
corresponded to new-borns for whom one or more of the following actions
were required: non-invasive or invasive ventilation (with face mask,
nasal cannula, or endotracheal intubation), chest compressions,
umbilical cord vein catheter insertion, or intravenous administration of
epinephrine.