Interpretation
A systematic review comparing forceps with ventouse delivery
demonstrated that forceps were less likely to fail than ventouse (OR
0.65, 95%CI 0.45-0.94), but forceps carried an increased risk of
maternal perineal trauma and there was a risk of neonatal injury with
the use of both instruments (facial injury for forceps, and
cephalohaematoma for ventouse) 18. This review did not
differentiate between rotational or direct forceps, and data was
insufficient to control for key confounding factors such as differences
in fetal position or station. Additionally, no trials currently exist
comparing primary emergency full dilatation Caesarean section with
instrumental delivery 19.
The method of delivery and choice of instrument is a complex decision
which represents a key dilemma for any obstetrician20. There is a multiplicity of factors to consider
including the exact position and station of the fetal head, the adequacy
of the female pelvis, the technique and experience of the operator and
the wishes of the mother 21; and the operator must
ensure the highest likelihood of successful delivery that will minimise
risk for both mother and fetus 6.
We aimed to investigate factors predisposing to successful or safe
delivery for delivery suite trials using regression analysis. Due to a
broad selection of confounding variables, we were unable to produce a
highly predictive model. Despite this, there were trends that can be
highlighted from the data: in the presence of experienced operators both
Keilland’s forceps and manual rotation plus direct forceps deliveries
were associated with a high rate of completion with no increase in
maternal or neonatal exposure to adverse perinatal outcome. Direct
forceps without rotation also had a high rate of completed delivery,
however this group had a very high proportion (74%) of babies in
occipito-anterior position and examination of the use of direct forceps
in babies with an occipito-posterior position demonstrated much lower
rates of completion and high rates of adverse outcome, particularly
maternal 3rd degree tear. Ventouse deliveries were
associated with the lowest completion rates (75%) and the highest rates
of composite risk outcome (29%), including high rates of
3rd degree tear and high rates of neonatal admission
to NNU. These rates are higher than those published in systematic review19 , perhaps due to the ‘intention to deliver’
analysis used in this study. It is notable from our data that 44% of
ventouse cases required the use of second instrument (usually direct
forceps) and therefore, in some cases, a woman undergoing attempted
ventouse delivery will have been exposed to a risk of the original
ventouse delivery, a risk of sequential instrument use and a further
risk of full dilatation Caesarean section.
Success or failure of any delivery attempt cannot be known a priori, and
therefore it is important for more studies to help guide clinicians in
clarifying the likelihood of successful delivery from the different
methods available, whilst minimising maternal and neonatal risks22. This is particularly important for delivery trials
performed in obstetric theatre as this is a situation that has already
been categorised by an operative decision maker as a potentially more
challenging delivery.
Conclusion:
This study adds to existing literature by investigating all types of
delivery mode available to an operator for full dilatation deliveries in
obstetric theatre and providing a comparison, adjusted for confounding
factors, of both the likelihood of success and the immediate risk of
such ‘trials’ to both mothers and babies. The data presented further
supports the notion that attempting instrumental delivery in delivery
suite theatre, as an alternative to primary emergency Caesarean section,
is both reasonable and safe. In this study, ventouse delivery was less
likely to achieve vaginal delivery than other methods of instrumental,
potentially exposing patients in some cases to the risks of more than
one form of delivery. There remains an urgent need for further research
to examine in detail the factors associated with likely completion of
instrumental delivery to allow obstetricians and women to make careful
informed decisions regarding a safe and successful delivery trial.