Induction & Augmentation Of Labour Flashcards
(16 cards)
Induction of labour
IOL refers to interventions designed to initiate labour prior to spontaneous onset with a view to achieving vaginal
delivery
b) Planned initiation of labour prior to its spontaneous onset after the period of viability by any method (medical,
surgical or combined) for the purpose of vaginal delivery.
c) Deliberate termination of preg beyond 28 wks by any means which aims at initiation of labour and vaginal delivery
Augmentation of labor
Is the process of stimulation of uterine contractions (both in frequency and intensity) that are already present but
found to be inadequate. Or is the artificial stimulation of labor that has begun spontaneously
Refers to enhancement of uterine contractility in women in whom labour has already started
Elective (Social) induction
Elective (Social) induction of labor means initiation of labor at term pregnancy without any acceptable medical or
obstetric indication. Done to satisfy the domestic and organizational needs of the woman and her family
Indications for induction of labor (IOL
a) Pre-eclampsia, eclampsia (PIH)
b) Maternal medical complications
i.) Diabetes mellitus
ii.) Chronic renal disease
iii.) Cholestasis of pregnancy
c) Postmaturity
d) Abruptio placenta
e) Intrauterine Growth Restriction (IUGR)
f) Unexplained antepartum haemorrhage
g) Rh-isoimmunization
h) Premature rupture of membranes
i) Fetus with a major congenital anomaly
j) Intrauterine death of the fetus
k) Oligohydramnios, polyhydramnios
l) Unstable lie-after correction into long. lie
m) Twin pregn continuing beyond 38 wks
Contraindications of induction of labor
a) Contracted pelvis and cephalopelvicdisproportion
b) Malpresentation (breech, transverse / oblique lie)
c) Prev classical C/S, hysterotomy, myomectomy
d) Uteroplacental factors:
i.) Unexplained vaginal bleeding, vasaprevia,
placenta previa
e) Active genital herpes infection
f) Breech presentation is a relative contraindication
g) High risk pregnancy with fetal compromise
h) Heart disease
i) Pelvic tumor
j) Elderly primigravida with obstetric or medical
complications
k) Umbilical cord prolapse
l) Cervical carcinoma
m) fetal distress
indications for Augmentation
a) Abnormal labor
(in the presence of
inadequate uterine
activity)
b) Prolonged latent
phase
c) Prolonged active
phase
Dangers of IOL
Maternal
a) Tendency of prolonged labor due to abnormal uterine action
b) Increased morbidity
c) Psychological morbidity, when there is induction failure and cesarean section is contemplated
d) Increased need of analgesia during labor
e) Increased operative interference
Fetal
a) Iatrogenic prematurity
b) Hypoxia due to disordered uterine action and operative interference
Factors for successful induction of labor
a) Period of gestation Pregnancy nearer the term or post-term — more the success.
As time of spontaneous labour approaches, cervix becomes softer, shortened, moves forward & starts to dilate.
b) Preinduction score Bishop Score ≥ 6 is favorable. Dilatation of the cervix is most important
c) Sensitivity of the uterus - Positive oxytocin sensitivity test is favorable for IOL
d) Cervical ripening - More successful in parous women & in cases with PROM than elderly primigravida and IUFD
e) Presence of fetal fibronectin in vaginal swab (> 50 ng/mL)- Favorable for successful IOL
what to do before inducing labour
A low bishop score ≤ 5 is “unripe” and unfavorable cervix
Before induction, do blood typing / grouping and save.
Check gestation, confirm presentation and exclude contraindications (e.g. placenta praevia).
Continuous electronic monitoring of the fetal heart rate and uterine activity is required during induction.
Take caution in previous caesarean section and uterine surgery (risk of uterine rupture), and grand
multiparity or previous precipitous labour (risk of hyperstimulation).
The cervix should be assessed using the modified Bishop’s scoring system
differentiate btwn cervical ripening, dilatation and effacement
Cervical Ripening- series of complex biochemical changes mediated by the hormones in the cervix which alter
cervical collagen and ground substances composition and ultimately cause it to becomes soft and pliable
Cervical dilatation relates with dilatation of the external os and effacement is determined by the length of the
cervical canal in the vagina.
It’s expressed either in terms of fingers-1, 2, 3 or fully dilated or better in terms of centimeters (10 cm when
fully dilated).
Measured with fingers but recorded in centimeters. One finger equals to 1.6 cm on average.
Cervical Effacement- process by which the muscular fibers of the cervix are pulled upward and merges with the
fibers of the lower uterine segment and lead to expulsion of mucus plug
Cervix becomes thin
Precedes dilatation of the cervix in primigravidae, whereas in multiparae, both occur simultaneously
Anterior lip of the cervix is the last to be effaced
Effacement of the cervix is expressed in terms of percentage, i.e. 25%, 50% or 100% (cervix less than 0.25 cm
rim’ is used when the depth of the cervical tissue surrounding the os is about 0.5–1 cm
Methods of cervical ripening
Pharmacological methods
a) Prostaglandins (PGs)
– Dinoprostone (PGE2): Gel, tablet, suppository
– Misoprostol (PGE1): Tablets.
b) Oxytocin
c) Progesterone receptor antagonists
– Mifepristone (RU 486)
d) Relaxin
e) Hyaluronic acid
f) Estrogen
Non-pharmacological methods
a) Stripping the membranes
b) Amniotomy (artificial rupture of the membranes)
c) Mechanical dilators, osmotic dilators (laminaria)
d) Transcervical balloon catheter
e) Use of bougies
f) Nipple stimulation
medical Methods of induction
a) Prostaglandins PGE2, PGE1
Act locally to cause myometrial contraction but PGE2 is primarily important for cervical ripening whereas
PGF 2α for myometrial contraction.
Intracervical application of dinoprostone (PGE2 – 0.5 mg) gel is the gold standard for cervical ripening
Give Misoprostol (PGE1), aka Cytotec- p.o / transvaginally / intracervical.
* It’s cheaper & easily stored than other PG.
* Dose: 25-100 mcg Intravaginal PGE (gel or tablets)- every 4 hrs, & a total 6-8 doses are used.
* Buccal / sublingual avoid first pass hepatic circulation & maintain serum bioavailability similar to that
of vaginal use
Prostaglandins have an advantage over oxytocin of decreased need for analgesia in labour, fewer cases
undelivered within 12 and 24 hours, decreased operative delivery
b) Oxytocin (Syntocinon)
Is an endogenous uterotonic that stimulates uterine contractions.
Oxytocin receptors are more in the fundal myometrium than in the cervix and tend to increase in
concentrations during pregnancy and in labor
Has a short half life (3-4 minutes) and so plasma levels fall rapidly when intravenous infusion is stopped
Dose: –may be given by pump. Start at
dose of 1-4 milliunits/min and increase (
titrated against contractions) up to a
maximum of 32 mU/Min. Dose of
oxytocin required to produce effective
uterine contraction is 4-16 Mu/min
Oxytocin is effective for induction of labor
when cervix is ripe & less effective as a
cervical ripening agent
Cause uterine hyperstimulation
c) Mifepristone
Mifepristone (progesterone receptor
antagonists) blocks both progesterone and glucocorticoid receptors
Dose: 200 mg vaginally OD for 2 days- ripen the cervix and induce labor.
Onapristone is a more selective progesterone receptor antagonists
surgical Methods of induction
a) Artificial rupture of the membranes (ARM)
ARM (amniotomy) is used to induce labour when cervix is favourable
and is also used for augmentation.
A well fitting presenting part is essential to prevent cord prolapse
ARM allows the presenting part to improve its application to the cervical
os
b) Stripping (sweeping) the membranes
Refers to the digital separation of the fetal (chorioamniotic) membranes from the
walls of the cervix and lower uterine segment prior to labour at term
Accelerate onset of labor by releasing endogenous PGs from membranes & decidua.
Manual exploration of cervix triggers Ferguson reflex which promotes oxytocin
release from maternal pituitary.
Criteria for membrane stripping are:
i) Fetal head must be well applied to the cervix
a) Cervix should be dilated so as to allow introduction of examiner’s fing
c) Mechanical dilators – significantly shorten the induction to delivery interval as compared
with no pre- induction ripening
Hygroscopic dilators e.g. laminaria (desiccated seaweed), lamicel (magnesium sulphate in polyvinyl
alcohol) act by absorption of water, swell and forcibly dilate the cervix and are as effective as PGE2
Act by release of endogenous prostaglandins from the membranes and maternal decidua to induce labor and
cervical ripening
Disadv: discomfort both at the time of insertion and with progressive cervical dilatation
d) Transcervical Balloon Catheter (Foley catheter) is effective for cervical ripening
Inflate with maximal fluid up to 60cc water, wait for catheter to drop
* Mechanism of action
– Mechanical distension of cervix
– Local release of prostaglandins
– Stimulation of pituitary release of oxytocin (Ferguson`s reflex)
combined Methods of induction
Combined medical and surgical methods are commonly used to increase the efficacy of induction by
reducing the induction-delivery interval
a) Oxytocin infusion prior to or following ROM
b) With the head non-engaged, preferably induce with PGs gel or oxytocin infusion followed by ARM
Risks of induction of labour
- Greater pain in labour
- Uterine hyperstimulation
- Cord prolapse
- Greater risk of uterine rupture during VBAC
- Failure
- Increased need for Caesarean or instrumental
delivery - Fetal compromise
Complications of induction of labour
- More pain with an induced labour
- Prolonged labours augmented with oxytocin predispose to
PPH 20
to uterine atony - Fetal compromise due to uterine hyperstimulation
- Cord prolapse- If ARM is performed while fetal head is high
- Creater risk of uterine rupture
- Failure of induction of labour
