normal birth mechanism - aiims, rishikesh

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