INSTRUMENTAL VAGINAL
DELIVERY
INTRODUCTION: Although the use of instrument to facilitate
a birth was initially reserved for the extractor of dead infants via
destuctiver technique, there exist reports from as early as 1500 B.C & of
successful deliveries of live infants in obstructed labour.
Peter
chamber lens development of the modern obstetric forceps in the late 16th century
dramatically changed the aim of
intraspartum intervention in favour of delivery of a live baby, and following
from Williams Smellegs description of the use of forceps in mid- wives,
instrumental intervention in the process of labour has become a more widely
accepted practice.
Between 1st April, 1998 & 31st march,
1999, 11.3% of all deliveries recorded in u.k were assisted with either forceps
or vacuum. However, the incidence of instrumental intervention varies widely
both within &between countries, and may be performed as infrequently as
1.5% or as often as 26% of cases. Such differences may often be related to
variation in the most of patients in the labor ward.
STRATEGIES FOE
REDUCING THR NEED FOR INSRUMENTAL VAGINAL DELIVERY
1. Provision
of a care giver in labour. This is associated with a reduction in the need for
operative vaginal deliveries (odds ratio 0.77). The effect is seen in women who
are both accompanied or unaccompanied by a family member.
2. Active
management of the 2nd stage with syntocinon in nulliparous women
with the use of epidural analgesia.
3. Delayed
pushing in nulliparous women with epidural, analgesia. It is the also important
to recognize that the chance of a spontaneous delivery is slightly more common
among women who delay pushing.
Other
techniques that are commonly used include:
4. The
use of upright positions in labour.
5.
Allowing epidural analgesia to wear off before asking her to push.
Operative
vaginal delivery has clearly identified as a major risk factor for fortal
morbidity &mortality, as well as for early and late maternal morbidity,(including
faucal incontinence).
INDICATIONS
FOR ASSISTED VAGINAL DELIVERY.
FOETAL INDICATIONS
1. Malpositioning
of the foetal head(occipitotransverse&occipito posterior)
2. foetal
distress
3. Delivery
of pre-term infants(weight<1.5kg)
MATERNAL INDICATION
1. maternal
distress
2. maternal
exhaustion
3. Undue
prolongation of 2nd stage of labour.
Labour may be deemed to be
prolonged if the 2nd stage last more than 2 hours in a primigravida(3hours if an epidural is in
situ)or more than 1 hour in a multipart(2hrs if epidural is in situ)
4. Medically significant conditions, e.g.
Aortic value dz with significant outflow obstruction or myasthenia gravis.
INSTRUMENTS
CHOICE AND MANAGEMENT OPTIONS
The choice of instruments employed by the Accoucher
should be based on the combination of:
a.
Indication
b. Experience
c.
Training
It
is certainly the case that only adequately trained or supervised practitioners
should undertake any vacuum or forceps delivery.
Systematic
review has shown the vacuum extractor, when compared to the forceps, to be
siginifically more likely to:
a.
fail at achieving a vaginal delivery
b. Be
associated with cephalhaematoma
c.
Be associated with retinal hemorrhaged
d. Be
associated with maternal worries about the baby
Significantly less likely associated
with
a.
Use of maternal regional / general
anesthesia
b. Significant
maternal vaginal or perinea trauma
c.
Severe perinea pain at 24hrs
And equally likely to be associated with
a.
Delivery by cs
b.
Low 5-minutes Apgar scores
c.
The need for phototherapy (neonatal
jaundice from cephalhaematoma)
The incidence of maternal injuries in
deliveries performed with the vacuum is significantly reduced compared with
forceps. Anal sphincter injuries are twice as companion in forceps deliveries.
PREREQUISITES FOR INSRUMENTAL DELIVERY
1. The
membrane must be ruptured
2. The
cervix must be fully dilated(8cm in
ventous)
3. The
head must be presenting.
4. The
presenting part should be at station +1 or more below the spine.
5. Adequate
analgesia/ anesthesia (not necessary in ventus)
6. The
bladder must be empty.
7. The
operator must be knowledgeable and experienced, with adequate preparation to
proceed with an alternative approach if necessary.
8. An
adequate informed and consented patient (not necessary a written consent).
9. For
forceps, it is essential that the operator checks the pair of forceps to ensure
that a matching pair has been provided, and that the blades lock with ease.
CONTRAINDICATION
The ventous should not be used:
1. After-coming
head of the breech
2. In
cases where multiple scalp punctures have been done during foetal intra-partum
monitoring
3. Gestation
less than 32wks.
4. Cases
of face presentation
INSTRUMENTS.
The ventous/vacuum extractors: the basic premise of such instruments is that
a s
Suction cup, of a slastic bird
modification or rigid malsroms’s construction,(medical is annected ,via tubing
to a vacuum source. Either directly through the Tubing, or via the connecting
chain, direct traction can then BE applied to the presenting part to expedite
delivery recent developments have removed the need for cumbersome external
sucken generactors, and have incerporated the vacuum mechanism into hand-held
pumps, e.g Omni cup.
The malstroms‘cup is made up of 4cm and 5cm
cups, but the bird’s modification has introduced the 2cm cup&posterior cup
(for occipito posterior positions)
The operating vacuum pressure for nearly
all ventous is b/w 0.6-0.8kg/cm2.for successful use of the ventous, determination
of the flexion point is vital. This is located at the vertex which, in an
average term infant, is on the segital suttire; 3cm anterior to the
posteriorfontanelle.the centre of the cup should be positioned directly over
this, as failure to do this will lead to a progressive deflection of the foetal
head during fraction and inability to deliver the baby. One can either use a
step-wise increase in the vacuum pressure, or a linear increase. Using the
linear increase in the pressuretechniquewith a slastic cup, caput succedaneums
formed instantly and with ametal cup, an adequate chignon is produced in less
than 2mins. The standard teaching has been that the largest cup that can be
placed should be used. However, in practice, a 5cm cup is usually suitable for
nearly all deliveries. It is prudent to I crease the suction to o.2k/cm2first,
and then to re-check that no maternal tissue is caught under the cup edge. When
this is confirmed, the suction can then be increased.
Traction must occur
in the plane of least resistance along the axis of the pelvis-the traction
plane. This will usually be at exactly 900 to the cup, and the
operator should keep a thumb and for finger on the cup at the traction
insertion, to ensure that the traction direction is correct to feel for
slippage. Safe and gentle traction is then applied in concert with uterine
contractions and voluntary expulsive efforts. This minimizes undue traction,
and the risk of trauma to the foetus. With the ventose, the operator should allow
no more than 2 episodes of breaking the suction in any vacuum delivery, and the
maximum time from application to delivery should ideally be < 15 minutes. If
there is no evidence of descent with the first pull, the patient should be
re-assessed to ascertain the reason for failure to progress. This may be due to
2 main reasons.
a.
Leakage of instrument
b.
Significant (large) output
Other
reasons include:
c.
Inclusion of maternal soft tissue
within the cup.
d.
Misdiagnosis of the position of foctal
head with incorrect equipment placement
e.
Choice of wrong instrument
f.
Undetected CRD
Rotation is achieved by the natural progression of the head through the pelvis. The operator must never must never try to assist rotation by manually turning the cup, as this is unhelpful, and can lead to severe scalp laceration.
Rotation is achieved by the natural progression of the head through the pelvis. The operator must never must never try to assist rotation by manually turning the cup, as this is unhelpful, and can lead to severe scalp laceration.
FAILED
VENTOUSE
Application
and slipping off of the ventus for 2 times or for more than 15 minutes without
delivery is referred to as failed ventouse.
TYPES OF FORCEPS
The
basic forceps design has not radically changed over many years and all types in
use today consists of two blades with sharks, joined together at a lock, with
handles to provide a point for traction. The blades may be fenestrated (open)
pseudotenestrated (open with a protruding ridge) or solid. Likewise, the length
of the shanks, the design of the locks (divergent, convergent, or sliding), and
or the flashing of the handles, are instrument specific.
TECHNIQUE:
Once
the patient has been optimally positioned, the pelvis must be examined the
position and situation of the vertex and the contours of the pelvis. The
forceps should then be held in front of the patient so as to visualize how they
will be inserted per vaginum, and placed around the foetal head. It is
appropriate to use non rotational forceps when the head is occipito – anterior
in position +15o. When the head is positioned >15 o
from the vertical, rotation must be accomplished by rotation manually. By
convention, the left blade should be inserted before the right, with the
Accoucheur’s hand protecting the vagina wall from direct trauma. With proper
placement of the forceps’ blades, they come to lie parallel to the axis of the
foetal head and between the foetal head and the pelvic wall. The operator then
articulates and locks the blades, checking the application before applying
traction. If the application is not correct, the blades must be repositioned
Traction
must be applied intermittently in concept with uterine contractions and
maternal expulsive efforts. The axis of traction changes during the delivery
and is guided along the J-shaped curve of the pelvic. As the head begins to
crown, the blades are directed to the vertical, Ritgen maneuver is performed or
an episotomy fashioned. Once the head is delivered, the forceps are removed in
the reverse order to which they were inserted, and the delivery is completed in
the normal fashion.
Kjelland’s
forceps are the most commonly utilized instruments for rotational forceps
deliveries and, as specific techniques are required, only those who have been properly
trained for their use should employ them.
Forceps
delivery is classified into 3:
1. High
forceps
2. Mid
cavity forceps
3. Outlet
forceps (eg Wriglegs, Kjelland’s)
FAILED
FORCEPS
Once the forceps is
applied twice without delivery, it is said to have failed.
Reasons include:
1.
Poor assembly
2.
Mid – application
3.
Unsuspected CRD
Ritgen maneourver –
Delivery of a child’s head by pressure on the perineum while control the speed
of delivery by pressure with the other head on the head.
Crowning – that stage
of childbirth when the foetal has negotiated the pelvic outlet and the largest
diameter of the head is encircled by the valva ring.
SYMPHSIOTOMY
This means separation
of the sympholisis pubis to allow the delivery of a baby in cases of obstructed
labour where the facilities for CS do not exist (and the centers with the
facilities are not easily accessible). It can lead to a 2-3cm increases in the
bony pelvic diameters, However, there is a significant risk of long term
maternal morbidity. Special skills and equipment are required, including a
solid bladed scapel. The urthra must be cathetaried and displaced laterally. In
the absence of an epidural, local anesthesia is needed. It is likely that the
foetus would have been severely compromised bt the time a symphsiotomy would be
safely performed. Make sure the baby is still alive.
COMPLICATIONS
1.
Gait instability
2.
Ostitis pubis
3.
chronic pelvic pain
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July 08, 2015
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