Normal Birth Mechanism - AIIMS, Rishikesh
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Normal Birth Mechanism
Prasuna Jelly
College of Nursing
AIIMS Rishikesh
➢Forceps
➢Ventouse
➢Destructive operations
➢Manual removal of placenta
Any delivery process which is assisted by vaginal
operations
Introduction• Incidence of Operative Vaginal Delivery(OVD)–10-15%
– % of forceps declining compared with vacuum
extraction
– Geographic differences
• Lowest in the Northeast
• Highest in the South
A study shown that:1996
• Incidence: 4.5% of vaginal deliveries
• Forceps deliveries = 0.8%
• Vacuum deliveries = 3.7%
• Success Rate = 99%
– Reflects appropriate choice of candidates
*Bofill JA. Operative Vaginal Delivery: A survey of fellows of ACOG. 1996;88:1007
Indications for OVD
No indication is absolute
• Prolonged 2nd stage
– Nulliparous, Multiparous: lack of continuous
progress
• Fetal compromise➢ Failure of the fetal head to rotate
➢ Fetal distress
➢Control of the fetal head in vaginal beech delivery
• Maternal benefit to shortened 2nd stage
• Elective forceps
Things to know:
Station
Positions above the ischial spines
are referred to as -1 through -5
As the head descends past the
ischial spines, the stations are
referred to as +1 through +5
(head visible at the introitus).
At the 0 station, the fetal head is at the bony
ischial spines and fills the maternal sacrum.
Four Pelvic Types
Important Landmarks
What Do I Need To Know Before Attempting an
Operative Delivery?
Presentation
(Cephalic/Breech)
Position (i.e. occiput
posterior, sacrum
anterior)
Lie (longitudinal,
oblique, transverse)
Station
Presence of asyncliticism
Clinical pelvimetry
Anaesthesia
Prerequisites for OVD
• Informed consent
• Vertex
• Engaged
• ≥34 weeks (vacuum
delivery)
• Fully dilated
• Membranes ruptured
• Adequate maternal
pelvis
• Adequate anaesthesia
• Maternal - empty
bladder
• Backup plan
• Ongoing fetal and
maternal assessment
• Choice of operation:
Outlet, Low, Mid & High
Contraindication - OVD
• Non-cephalic, face or brow presentation
• Unengaged vertex
• Incompletely dilated cervix
• Clinical evidence of CPD
• < 34 weeks gestation (vacuum)
• Need for device rotation (vacuum)
• Deflexed attitude of fetal head
• Fetal conditions (e.g. thrombocytopenia)
Obstetric Forceps
• Obstetric forceps is a pair of instruments specially
designed to assist extraction of the fetal head and
there by accomplishing delivery of the fetus.
• MNEMONIC for F-O-R-C-E-P-S-
F- Favorable head position and station
O- Open Os (full dilatation)
R-Ruptured membranes
C- Contractions present & Consent
E- Engaged head, empty bladder
P- Pelvimetry, no major CPD
S- Stirrups; lothotomy position
Type of Forceps Delivery
• Outlet forceps– Scalp visible at introitus without separating labia
– Fetal skull reached pelvic floor & head at/on perineum
– Sagital suture in AP diameter or LOA, ROA, or posterior position
– rotation does not exceed 45º
• Low forceps– Leading point of fetal skull at >= +2, not on pelvic floor
– Rotation 45º or less (LOA/ROA to OA, or LOP/ROP to OP); or rotation greater than 45º.
Type of Forceps Delivery
• Mid forceps– Above +2 but head engaged
– Engagement has taken place and
the leading part of the head is
below the level of the ischial spines.
• High forceps– Head not engaged; not included in ACOG classification
– Not recommended
Types of application (of forceps blades)
• Cephalic application
• Pelvic application
Types of Forceps
Main types of forceps are:
• Long curved forceps
with or without axis
traction device
• Short curved forceps
(Wrigley's Forceps)
• Kielland’s forceps
Structure:Forceps have 4 major components, (Parts):
1. Blades
2. Shanks
3. Lock
4. Handles
Application of forceps
Williams Obstetrics - 22nd Ed. (2005)
Application of forceps
Williams Obstetrics - 22nd Ed. (2005)
Williams Obstetrics - 22nd Ed. (2005)
Williams Obstetrics - 22nd Ed. (2005)
Williams Obstetrics - 22nd Ed. (2005)
Forceps-Assisted Vaginal
Delivery(FAVD)
Identify & apply blades Place instrument in
front of pelvis with tip pointing up & pelvic curve forward
Apply left blade, guided by right hand, then right blade with left hand
Lock blades Should articulate with
ease
FAVD• Check for correct application
– Sagittal suture in midline of
shanks
– Cannot place more than one
fingertip between blade and
fetal head
• Apply traction
– Steady and intermittent
– Downward and then upward
– Remove blades as fetus
crowns
Technique of pull
LOW FORCEPS DELIVERY
After coming
Head
Trial forceps
• FAILED FORCEPS
1. Unsuspected disproportion.
2. Misdiagnosis of the position of the head.
3. Incomplete dilation of the cervix.
4. Outlet contraction (very rare in an otherwise
normal pelvis).
Risks: Forceps
Maternal Risks Perineal Injury (extension of
episiotomy)
Vaginal and Cervical lacerations
Postpartum hemorrhage
trauma to soft tissue 3rd/4th
degree double the risk compared to ventouse
bleeding from lacerations
trauma to urethra & bladder fistula
Pain 17%
Fetal Risks
➢ bruising & laceration to the face
➢ Injury to the fetal scalp
➢ cephalohematoma 9%
➢ retinal hemorrhage 30%
➢ skull fracture
➢ permanent nerve damage / Facial
nerve
➢ Intracranial hemorrhage
➢ Facial / Brachial palsy
The risk of shoulder dystocia is increased following
instrumental deliveries
Vacuum Extraction (Ventouse)
• Ventouse is a vacuum device used to assist the
delivery of a baby when labour has not
progressed adequately.
INDICATIONS
MATERNAL
• Exhaustion
• Prolonged second stage
• Cardiac / pulmonary disease
FETAL
• Failure of the fetal head to rotate
• Fetal distress
Contraindications
• Moderate or severe cephalopelvic
disproportion.
• Other presentations than vertex.
• Premature infants.
• Intact membranes.
• Known or suspected fetal macrosomia
• Overlapping cranial bones, heavy caput
• Face presentation or breech presentation
PREREQUISITES
Vacuum-Assisted Vaginal Delivery
• Do not apply rocking motion, only steady traction in the line of the birth canal
• Stop after: three “pop-offs” of vacuum, > 20 minutes elapsed, three pulls with no progress
Types of Vacuum cups
Insertion
Vacuum Placement
• Proper cup placement is the most
important determinant of success in
vacuum extraction.
• The center of the cup should be over the
sagittal suture and about 3 cm in front of
the posterior fontanelle toward the face.
Vacuum application:
After determining position of the head:
(A)insert the cup into the vaginal vault, ensuring that
no maternal tissues are trapped by the cup.
(B)Apply the cup to the flexion point 3 cm in front of
the posterior fontanel, centering the sagittal
suture.
(C)Pull during a contraction with a steady motion,
keeping the device at right angles to the plane of
the cup.
(D)Remove the cup when the fetal jaw is reachable
Procedure
• Lithotomy position.
• Antiseptic measures for the vagina, vulva and perineum.
• Vaginal examination to check pelvic examination.
• Application of the cup
• Creating the negative pressure
• Traction
• Release of the cup
• The head must be completely or partially delivered with no more than
3 pulls.
• The head is at least begin to move with the first pull.
• The cup must not be applied more than twice.
• Application of the cup must not exceed 20 minutes.
Vacuum
• After correct placement of the cup is confirmed,
vacuum pressure should be raised to 100 to 150
mmHg to maintain the cup's position.
• Vacuum suction pressures of 500 to 600 mmHg have
been recommended during traction.
• although pressures in excess of 450 mmHg are rarely
necessary.
• Between contractions, suction pressure can be fully
maintained or reduced to <200 mmHg
Types of vacuum application
Mid Pelvis
Pelvic Floor
Outlet
Axis Animation
Failed Procedures
• Reasons for failure:– CPD
– Incorrect technique• Traction w/o maternal pushing efforts
• Upward traction prior to crowning
– deflexing application
– Large caput succedaneum• Large volume of scalp into cup reduces the total
vacuum area
• More pronounced with bell compared to mushroom cups
• More pronounced with soft compared to rigid cups
Avoiding Problems
• Confirm cup placement
• Avoid entrapping vaginal soft tissue
• Know when to abandon the procedure
– Practitioners must be willing and able to abandon the
procedure and proceed to cesarean delivery promptly
when the vaginal delivery is not progressing normally.
Vacuum Use at Cesarean
Section
Fetal Risks: VAVD
Scalp lacerations: if torsion excessive
Cephalohematoma: limited to suture line
Subgleal hematoma: crosses suture line
Intracranial/retinal hemorrhage
Hyperbilirubinemia/jaundice
Higher incidence of cephalohematoma/retinal hemorrhage/jaundice compared to forceps
Risks with vacuum delivery:Swellings and Bleeds Associated With Operative Vaginal Delivery
Subgleal Hematoma
Using both forceps and vacuum
• Highest risk for injury is for combined
forceps/vacuum extraction or cesarean
delivery after failed operative delivery
• The weight of available evidence is against
multiple efforts with different instruments
Assignment on
• Advantages of Forceps over Ventouse
• Advantages of Ventouse over Forceps
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