INDUCTION AND INDUCTION AND

MECHANISM OFMECHANISM OF

LABOUR LABOURDr Ramya PathirajaDr Ramya Pathiraja

Senior LecturerSenior LecturerFaculty of Medical SciencesFaculty of Medical Sciences

University of Sri JayewardenepuraUniversity of Sri Jayewardenepura

objectivesobjectives• Diagnosis of labour• Stages of labour• Management of labour• Interpretation of CTG• Induction of labour• Oxytocic drugs

• Establishing the diagnosis of labour is the most basic and essential aspect of labour ward management

• Diagnosis of labour is based upon the onset of regular contractions, which are of increasing frequency and duration often associated with blood stained mucous show and less often rupture of membranes

• 10-15% neither woman nor the attendant can confirm whether or not they are in labour

• They should be reviewed over the next 2-6 hrs with repeat assessment of cervix

• Uterine contractions are recorded by frequency, duration and strength

• State of the cervix is recorded in terms of its position, effacement and dilatation

First stage of labourFirst stage of labour• Onset of regular painful uterine

contractions to effacement and full dilatation of the cervix

• There are three main components in the assessment and management of the 1st stage of labour

progress of labour condition of the mother condition of the fetus

• Main function of uterine contractions in the first stage of labour is cervical effacement and dilatation and to a lesser degree, descent of the presenting part

• Majority of the descent occurs in the second stage of labour

• Position of fetal head may be occipito anterior occipito posterior occipito transverse

• OP and OT positions are associated with varying degrees of deflexion which presents a larger diameter of the fetal head to the bony pelvis

• Asynclitism When one parietal bone presents at a

higher plane than the other when the head in the transverse position

as it enter the pelvis Anterior asynclitism is physiological and

posterior asynclitism indicate disproportion

• Caput Subjective assessment of oedema in the

scalp soft tissues + mild ++ moderate +++ severe

• Moulding

none bones normally separated + bones touching ++ bones overlapping but easily separated

with digital pressure +++ bones overlapping and not separable with digital pressure

• Station of the presenting part

Level of the lowest part of the fetal bony skull in relation to the ischial spines

With varying degrees of caput and moulding position may be difficult to asses

combined vaginal and abdominal assessment will be helpful

• If an incorrect diagnosis of labour is made when the woman is in spurious labour, a series of inappropriate interventions ( amniotomy, oxytocin augmentation, operative delivery) may ensure over and demoralising period

Charting the progress of labourCharting the progress of labour• Progress of labour frequency and duration of uterine contractions cervical effacement and dilatation descent of the presenting part

• Maternal conditions

BP, pulse ,temperature, and drugs administered

• fetal conditions

Colour and quantity of amniotic fluid

Fetal heart rate

partogrampartogram• Pictorial documentation of labour • Assures systematic and logical approach

• facilitate early recognition of poor progress

Rate of cervical dilatation has two phases

• A slow latent phase during which cervix shortens from 3cm in length to less than 0.5cm (effacement) and

dilates to 4 cm

• A faster active phase

Cervix dilates from 4 cm to full dilatation

• Alert line In order to identify those are at risk of

prolonged labour, a line of acceptable progress is drawn

• Action line Is drawn 4hrs to the right of the alert

line

• Interventions thought to be necessary if the rate of progress cut the action line

• Latent phase of labour last upto 8 hrs in nulliparous and 6hrs in multiparous

• In the active phase both nulliparous and multiparous women dilates at a rate of 1cm/hr with multi often dilates more rapidly

Upon admission to the labour roomUpon admission to the labour room

• Review antenatal record• Physical examination-GE, BP, abdomen, FHS • Urinalysis• VE- confirm the diagnosis of labour• If she is in labour, convey that to the

patient and if not send her back to the ward after an assuring CTG

During the 1During the 1stst stage stage

• Woman should be up and walking, encouraged to assume most comfortable position

• No woman in labour should be left alone• Explanation of progress and any

interventions should be carefully outlined to the woman and her partner

• Although there is enormous pressure on nursing and medical staff to chart all events for audit and medico legal purpose, a balance between this and the common sense, clinical care and communication must be achieved

Pain relief in labourPain relief in labour• Contnued support and explanation,

shortens labour, lessens the requirement for analgesia and reduces operative delivery

• Systemic narcotic analgesics pethidine 50-150mg IM IV pethidine and fentanyl

• As patient-controlled administration

• Inhalation analgesia-simple, safe, within limits and effective

Entonox 50%N2O 50%O2

• Epidural analgesia

MCQMCQ1. The active management of labour

includes

a. Induction of labourb. Acceleration of labourc. Use of a partogramd. A high caesarean section ratee. Continuous intrapartum fetal heart

monitoring

2. A partogram a. is a Pictorial documentation of labour b. Increase the incidence of operative deliver rate c. Assures systematic and logical approach d. facilitate early recognition of poor progress e. will increase the work load of the labour staff

summarysummary• Diagnosis• Terms – engagement, position,

caput,moulding • Partogram• Pain relief• First stage

Non-progressive labourNon-progressive labour• Powers• Passages• Passenger

often non progression is caused by combination of all three

• Augmentation of labour Amniotomy Oxytocin infusion

Ineffective uterine contractionRelative disproportion

• Non progressive labour is a trying event for all concerned.

• Care during labour should be directed towards sustaining the morale of the women and her partner

• maintaining maternal hydration and providing adequate analgesia

Second stage of labourSecond stage of labour• Full dilation of the cervix to delivery of the

infant

• second stage has two phases

passive phase (pelvic phase)

Active phase (perineal phase)

passive phase (pelvic phase)

full dilatation of cervix to descend of the head to the pelvic floor

• Multiparous – passive phase is very brief 30 mts

• Nulliparous- more time is required for descend. 60 mts

•

• Active phase (perineal phase)

bearing down effort of the mother begins

• Effect of epidural spontaneous labour, endogenous production of

oxytocin increased which augment uterine contractions causing descend of the presenting part

physiological increase is blocked by epidural due to interruption of Ferguson’s reflex

With epidural, augmentation with oxytocin is

necessary

• Epidural blunts maternal bearing down reflex

Epidural with selective sensory block and

augmentation with oxytocin will reduce prolonged second stage and incidence of assisted delivery

Length of second stage is influenced byLength of second stage is influenced by

• Parity• Fetal weight• Malposition (deflexed, OP, OT)• Maternal effort• Uerine contractions• Epidural

• Assessment of progress of labour

Combined vaginal and abdominal examination

• Maternal position during labour

Woman’s own choice Worst position is supine Upright position- more comfortable and logical Change position during labour Many will choose semi-recumbent position

Maternal bearing downMaternal bearing down• When to start ? Nulliparous - full dilatation occurs when

head at mid pelvis Unproductive, demoralizing, exhausting• How ? Valsalva maneuver• Bad effects ? FHR abnormalities Low cord PH Low Apgar score

Fetal surveillance in labourFetal surveillance in labour

4th confidential inquiry into stillbirths and deaths in infancy (CISD) highlighted the need for good fetal surveillance in labour

• Suboptimal interpretation of intrapartum CTG

• inappropriate action • poor communication were highlighted

• Cerebral palsy attribute to 25%-30% of intrapartum events in term pregnancies

Fetal heart rate monitoringFetal heart rate monitoring

Intermittent auscultation or continuous fetal heart rate monitoring (CTG) ?

• Intermittent auscultation for 1 mt through uterine contraction every 15 mts during 1st stage of labour and

after every other contraction OR every 5 mts in the 2nd stage of labour

Cont CTG is used • If auscultation shows changes in

baseline rate, decelerations, irregular heart rate

• difficulty in listening • all high risk labours

Indications for cont CTGIndications for cont CTG

Intrapartum

• Oxytocin augmentation• Epidural• Vaginal bleeding in labour• Maternal pyrexia• Fresh meconium

CTG - Basic considerationsCTG - Basic considerations

• Baseline heart rate

Calculated by drawing a line through the variability of the trace where there are no acclerations or decelerations

110 – 160 bpm

baseline variabilitybaseline variability• represents the integrity of the ANS bandwith of the up and down excursions or

“wiggliness” of the trace 5 – 25 bpm

Reduced < 5 bpmSuspicious CTG reduced longer than 40mts

but less than 90 mts Abnormal CTG Reduced longer than 90 mts

AcclerationsAcclerations• A rise in the baseline rate by more than 15

beats lasting for more than 15 sec

• Associated with fetal movements or other fetal stimulation by uterine contractions or pelvic examination

• Functioning CNS are necessary for FM

• Acclerations and normal baseline variability are hallmarks of normal fetal oxygenation

DecelerationsDecelerations• Drop in the baseline rate of more than 15

beats for longer than 15 sec

• Decelerations last less than 30 sec and immediately following an accleration are normal reflex changes in FHR

• Two types early decelerations mirror the contractions occur in late first and second

stage are vagally mediated

not due to hypoxia late decelerations due to hypoxia

Important points to consider Important points to consider • Accelerations and normal baseline variability

are hallmarks of fetal health• Accelerations with reduced baseline

variability should be considered suspicious• Period of decreased variability may represent

fetal sleep• Hypoxic fetus may have normal baseline heart

rate with no accelerations and reduced baseline variability

• Placental abruption, cord prolapse and scar rupture can give rise to acute hypoxia should be identified clinically

• Hypoxia and acidosis develop faster with abnormal trace in patients with scanty thick meconium, IUGR, intrauterine infection and those who are pre or post term

• In pre term, hypoxia and acidosis can predispose to hyaline membrane disease, RDS and may contribute to IVH – early action in the presence of abnormal trace

• Injudicious use of oxytocin, epidural anesthesia and difficult deliveries worsen hypoxia

• During labour if decelerations are absent asphyxia is unlikely

• Abnormal patterns may represent not only hypoxia, but also effects of drugs, fetal anomaly, infection, cerebral haemorrhage

Patterns of fetal hypoxiaPatterns of fetal hypoxiaHypoxia can gradually develop

due to repeated occlusion of the cord (manifest by variable decelerations)

decreased perfusion of the retroplacental intervillous space reducing the oxygen exchange during contractions (manifest by late decelerations )

• Hypoxia is unlikely to develop during labour without FHR decelerations

• Decelerations in the absence of rise in BHR or reduction n the baseline variability indicate cord compression or reduced uteroplacental perfusion

• With repeated frequent decelerations one of the first sign that indicate fetal hypoxia is the cessation of accelerations

• Fetus responds to hypoxia by increasing the HR to circulate more blood through placenta in an effort to get more oxygen

• Thus with increasing hypoxia, there is an increase in baseline HR until it reaches a plateau

STRESS TO DISTRESS INTERVAL • With baseline tachycardia, there is a

gradual reduction in baseline variability

• Combination of stable tachycardia with silent or flat baseline variability indicate that fetal ANS is probably hypoxaemic

DISTRESS PERIOD No intervention within a reasonable

time fetus may born with hypoxia and acidosis

• If the situation is ignored FHR decline rapidly leading to terminal bradycarda

DISTRESS TO DEATH INTERVAL can be quite short 20- 60 mts

Chronic hypoxiaChronic hypoxia• Pre existing hypoxia before the onset

of labour• Non reactive trace with reduce or

absent baseline variability together with shallow decelerations of < 15 bpm

• Which may start with uterine contractions but not recover until after the contraction is over

• Combination of shallow decelerations with absent baseline variability is the most ominous

• They may have normal BHR or mild tachycardia

• These fetuses can deteriorate and die within a short time with the stress of contractions

• Early delivery is indicated

Acute hypoxiaAcute hypoxia• Placental abruption• Uterine rupture and scar dehiscence• Cord prolapse• Epidural analgesia• Uterine hyperstimulation Hypoxia and acidosis are likely to occur

if bradycardia cont > 10 mts

• Immediate delivery in the presence of obvious cause

• Repositioning the woman• Stop oxytocin infusion• Tocolysis - terbutaline 0.25 mg SC/IV in

5 ml saline over 5 mts

Third stage of labourThird stage of labour• Birth of infant until delivery of placenta• Usually lasts 5-10 mts rarely more than 30

mts• Shortest of all three stages but carries most

potential risk for the mother• Placental separation• haemostasis

Signs of placental separationSigns of placental separation• Rising of uterine fundus and change from

broad discoid shape to a more narrow globular form

• Gush of blood from the vagina

• Cord lengthening of 8-15 cm- reliable sign

Management of third stage of labourManagement of third stage of labour• Expectant management Normal physiological changes to bring about

placental seperation Not effective• Active management Oxytocic drug with anterior shoulder induce

early and consistent uterine contractions PPH, blood loss and need for blood transfusion

are all reduced by 40-50%

Factors influence risk of inductionFactors influence risk of induction

• Fetal maturity• Parity• State of the cervix• Additional factors - CS

Modified Bishop ScoreModified Bishop Score

Pelvic score

0 1 2 3

Position of cervix

posterior middle anterior

Length of cervix cm

>4 3 1-2 <1

Dilatation of cervix cm

0 1-2 3-4 >4

Consistancy of cervix

Firm medium soft

Station of oresenting

part

-3 -2 -1/0 +1/+2

MCQMCQ• The active management of labour

includesa. Induction of labourb. Augmentation of labourc. Use of partogramd. A high LSCS ratee. Continuous intrapartum fetal heart

rate monitoring

• Ergometrine

A is given in dose of 250-500 micro gramsB is combined with oxytocin in syntometrineC should not be given to hypertensive

patientsD act within 60 sec if given IVE causes vomiting