BUKOVINIAN STATE MEDICAL UNIVERSITY
“Approved”
on methodological meeting
of Department of Obstetrics and Gynecology
with course of Infant and Adolescent Gynecology
“___”______________________ 201_ year
protocol #
T.a. The Head of the department
Professor
________________ O. Andriyets
METHODOLOGICAL INSTRUCTION
for practical lesson
“Uterus activity anomalies”
MODULE 4: Obstetrics and gynecology
CONTEXT MODULE 9: Pathological flow of pregnancy, labor and puerperium
Subject: Obstetrics and Gynecology
6th year of studying
2nd medical faculty
Number of academic hours – 6
Methodological instruction developed by:
ass.prof. Andriy Berbets
Chernivtsi – 2010
Aim: to learn the causes, clinic, diagnostic, treatment and preventing measures of abnormalities of
uterine contractions.
Basic level:
1. Estimation of normal uterine contractions.
2. Medicines which are used for normalization of uterine contractions
STUDENTS' INDEPENDENT STUDY PROGRAM
I. Objectives for Students' Independent Studies
You should prepare for the practical class using the existing textbooks and lectures. Special
attention should be paid to the following:
1. Obstetrics terminology.
2. External and internal obstetric examination.
3. Segments of fetal head
4. Lower segment of uterine and contraction ring.
5. Signs of normal uterine contractions
6. Conduct of normal labor & delivery and their clinic.
7. Classification of uterine contractions abnormalities.
8. Factors that provide normal uterine contractions.
9. Definition of primary and secondary uterine inertia.
10. Incoordinative uterine activity,
11. Excessive uterine activity.
12. Medicines for correction of uterine contractions.
13. Methods of treatment of uterine inertia in the first and second stages of labor.
14. Prevention of uterine contractions abnormalities.
Key words and phrases: uterine dysfunction, hypotonic and hypertonic, incoordinative,
excessive uterine activity.
UTERINE BIRTH ACTIVITY ANOMALIES
Birth activity anomaly is the state when frequency, duration, rhythm and force of parodynia
and labor do not provide dynamic, within the physiological parameters of time, advancement of
the fetus and its expulsion without delivery biomechanism violation.
Disorders of any index of uterine activity are possible — uterine tone, rhythm, frequency
and coordination of contractions, intervals between labor pains, delivery duration.
Correct diagnosis and management of abnormal labor requires evaluation of the
mechanisms of labor: in classic terms, the "power," the "passanger,"an the "passage,"
otherwise refferred to as the uterine contractions, fetal factors (e.g., presentation, size), and the
maternal pelvis, respectively: power, or strength, duration and frequency of uterine
contractions, evaluated both qualitatively and quantitatively. Frequency and duration of
contractions can be subjectively evaluated by manual palpation of the maternal abdomen
during contraction. Strength of uterine contractions is often judged by how much the uterine
wall can be "indented" by an examiner's finger during a contraction: strong contraction no
indetation; moderate contraction, some indentation; mild contraction, considerable
indentation. Although subjective, such determinations by experienced examiner are of value.
The frequency and duration of uterine tractions may be measured more accurately by using a
tocodynamometer while performing external electronic fetal monitoring.
For cervical dilatation to occur, each contraction must generate at least 25 mm Hg of
pressure, with 50 to 60 mm Hg being considered the optimal intrauterine pressure. The
frequency of contractions is also important in generating a normal labor pattern; a minimum
of three contractions in a 10- minute widow is usually considered adequuate.
During the first stage of labor, arrest of labor should not be diagnosed until the cervix is at
least 4 cm dilated ( i.e., the latent phase of labor has been completed) and a pattern of uterine
contractions that is adequate both in frequency and intensity has been established.
The early part, or latent phase, of labor is involved with softening and effacement of the
cervix with minimal dilatation. This is followed by a more rapid rate of cervical dilatation,
known as the active phase of labor, which is further divided into acceleration and deceleration
phases.
The descent of the fetal presenting part usually begins during the active phase of labor,
than progresses at more rapid rate toward after the cervix is completely dilated. A useful
method for assessing the progress of labor and detecting abnormalities in a timely manner is to
plot the rate of cervical dilatation and descent of the fetal presenting part.
Normal cervical dilatation and descent of the fetus take place in a progressive manner and
occur within a well-defined time period. Dysfunctional labor occurs when rates of dilatation
and descent exceed these time limits.
The normal limits of the latent phase of labor extend up to 20 hours for nulliparous patients
and up to 14 hours for multiparous patients. A latent phase that exceeds these limits is
considered prolonged and may be caused by hypertonic uterine contractions, premature or
excessive use of sedatives or analgesics, or hypotonic. uterine contractions.
Hypertonic contractions are ineffective, painful and are associated with increased uterine
tone, whereas hypotonic contractions are usually less painful and are characterized by an
easily indictable uterus during the contractions.
Hypotonic contractions occur more frequently during the active phase of labor. A long,
closed, firm cervix requires more time to efface and to undergo early dilatation than does a
soft, partially effaced cervix, but it is doubtful that a cervical factor alone causes a prolonged
latent phase. Some patients who appear to be developing a prolonged latent phase are shown
eventually to be in false labor, with no progressive dilatation of the cervix.
Palpation or recording of uterine contractions and observation of the patient over a period
of time usually suggests whether uterine activity is hypotonic or hypertonic or whether the
patient is in false labor.
The management of a prolonged latent phase depends on its cause. A prolonged latent
phase caused by premature or excessive use of sedation or analgesia usually resolves
spontaneously after the effects of the medication have disappeared. Hypertonic activity
responds erratically to oxytocin but usually responds to a therapeutic rest with morphine
sulfate or an equivalent drug.
Hypo contractile dysfunction usually responds well to an intravenous oxytocin infusion.
When the cervix dilates to approximately 3 to 4 cm, the rate of dilatation progresses more
rapidly. Cervical dilatation of less than 1.2 cm/hour in nulliparous women constitutes a
protraction disorder of the active phase of labor. During the latter part of the of the active
phase, the fetal presenting part also descends more rapidly through the pelvis and continues to
descend | through the second stage of labor. A rate of descent of presenting part of less than l.0
cm/hour in nulliparous women and 2.0cm/hour in multiparous women is considered to be a
protraction disorder of descent.
During the second stage of labor, the "powers" include both the uterine contractile forces
and voluntary maternal expulsive efforts (pushing). Maternal exhaustion, excessive
anesthesia, or other conditions such as cardiac disease or neuromuscular disease may already
affect these combined forces so that they are insufficient to result in vaginal delivery or
cesarean section may then be required.
In the absence of cephalopelvic disproportion or fetal malposition, protraction or arrest
disorders are usually caused by hypotonic uterine; contractions, conductions anesthesia, or
excessive sedation.
A prolonged latent phase can be managed by either rest or augmentation of labor with
intravenous oxytocin once mechanical factors have been ruled out. If the patient is allowed to
rest, one of the following will occur; she will cease having contractions, in which case she is
not in labor; she will go into active labor; or she will continue as before, in which case
oxytocin may be administered to augment the uterine contractions. The use of arnniotomy, or
artificial rupture of membranes, is also advocated [or patients with prolonged latent phase.
During the active phase of labor, mechanical factors such as fetal malposition and
malpresentation as well as fetopelvic disproportion must be considered before augmentation
of uterine contractions with oxytocin. In cases in which the fetus fails to descend in case of
adequate contractions, disproportion is likely and cesarean section warranted. If no
disproportion is present, oxytocin can be used if uterine contractions are judged to be
inadequate. In cases of maternal exhaustion resulting in secondary arrest of dilatation, rest
followed by augmentation with oxytocin is often effective.
Classification of birth activity anomalies:
I. Pathological preliminary period (false labor).
II Powerless labor (hypoactivity or inertness of the uterus):
1) primary;
2) secondary;
3) parodynia weakness: a) primary; b) secondary.
III.Excessively strong birth activity (uterine hyperactivity).
IV.Discoordinated birth activity:
1) discoordination;
2) hypertone of the inferior uterine segment (reverse gradient, inversion);
3) uterine tetanus (spasmodic labor pains);
4) circular dystocia (contraction ring).
1. PATHOLOGICAL PRELIMINARY PERIOD
The preliminary period is observed in 33 % pregnant women at the term of pregnancy of
38—40 weeks. The normal preliminary period is characterised by infrequent, weak spasmodic
pain in the underbelly and loin, which appears against the background of normal uterine tone.
Its duration may reach 6—8 h. Mature neck of uterus is diagnosed in 87 % women.
The pathological preliminary period is characterised by painful, intermittent by force and
sensation dilating pains, which arise against the background of increased uterine tone. The
pains are similar to labor pains, but do not lead to structural changes and cervical dilatation.
The pains stimulate the pregnant woman, lead to the violation.
of the diurnal sleep rhythm and total activity. The duration of pathological preliminary
period makes more than 8—12 h.
The pathological preliminary period is observed in women with functional changes of
central nervous system regulation (fear of labor, neurosis), neurocirculatory dystonia,
endocrine system malfunction, vegetative disorders. The pathological preliminary period may
directly turn into uterine inertia.
Treatment:
— sedatives and debilitants (diazepam, promedol);
— if it is ineffective — single-stage application of tocolytic therapy with beta-adrenoceptor
agonists (hexoprenalin 25 mg (5 ml) diluted in 500 ml of sodium chloride isotonic solution and
introduced i.v. drop-by-drop slowly 10—15 drops per min);
— preparation to delivery by intravaginal introduction of prostaglandin E2.
Contraindications to beta-adrenoceptor agonists application:
— hypersensitivity;
— premature placenta detachment;
— uterine hemorrhage;
— endometritis;
— extragenital pathology at decompensation stage;
— myocarditis;
— hyperthyroidism;
— glaucoma.
Side effects of beta-adrenoceptor agonists: headache; vertigo; tremor; tachycardia;
ventricular extrasystole; heart pains, ABP reduction.
If tachycardia arises (>100 bprn), introduction of verapamil and potassium preparations is
administered to the parturient woman.
2. POWERLESS LABOR (WEAK UTERINE CONTRACTIONS)
Powerless labor (PL) is a condition with insufficient intensity, duration and frequency of
labor pains, therefore smoothing, dilation of the uterine neck and fetus advancement at its
correspondence with pelvic dimensions are decelerated.
There are differentiated primary and secondary types of PL. Primary PL arises at the very
beginning of delivery and lasts during the period of dilation. PL arising after a period of longterm regular birth activity and manifesting itself with typical signs indicated above is called
secondary.
PL may be diagnosed during 4—6 h of clinical observation and during 2 h if hystcrography
is possible.
Excessively intensive birth activity develops unexpectedly. Strong labor pains take place in
a short interval of time, uterine contractions frequency is more than 5 in 10 min, which
promotes quick and sufficient dilation of the uterine orifice.
Parturition is considered rapid if it lasts less than 6 h in pri-mipara women and 4 h in
secundipara women, and accelerated — less than 4 and 2 h accordingly. Such types of
delivery cause injuries of the uterus and fetus (deep ruptures of the uterus, vagina, perineum,
premature detachment of normally located placenta, hypotonic bleeding, cord rupture, cerebral
hemorrhage, cephalohcmato-mas).
Treatment:
1. Oxytocin (deaminooxytocin or sandost, sandopard 25—50 IU, in. the active phase only) or
preparation containing oxytocin (pituit-rin, hyphotocin, mammophysin).
2. Prostaglandin E2 (dinoproston, prostin E2, prostarmon E, menzaprost-1) 0.5 mg — pills, 5 ml
— ampoules (before 4 cm cervical dilation).
3. P-adrenoceptor blocking agents (obsidan, propranolol) 5 mg/400 ml of physiological solution.
4. Aprophen (1 % — 1 ml) — peripheral and central M- and 11-anticholinergic drug — relaxes
the neck of uterus, intensifies uterine contractions.
5. Ozonized transfusion media.
6. Cesarean section if uterine inertia is combined with fetal hypoxia.
3. DISCOORDINATED BIRTH ACTIVITY
The frequency of discoordinated birth activity (DBA) makes 1-3%. There are no
coordinated contractions in different uterine parts (right and left, superior and inferior parts,
violation between uterine parts up to fibrillation and tetanus). It usually develops at the 1st
stage of delivery till the uterine neck dilates to 5— 6 cm.
The clinical picture is characterised by the hypertone of the inferior segment, irregular,
strong, sharply painful parodynia that reminds the picture of threatening hysterorrhexis.
Clinical signs:
— pain;
— violated rhythm of labor pains;
— no dynamics of cervical dilation;
— no head advancement;
— hypertone of the inferior uterine segment (reverse gradient);
— spasmodic parodynia (uterine tetany);
— dystonia of the neck of uterus.
The character of birth activity is detected on the basis of quantitative assessment of the
three main processes:
1) dynamics of uterine contractions;
2) dynamics of cervical dilation;
3) dynamics of the advancement of the presenting part of the fetus along the parturient canal.
Assessment methods:
1.Uterine activity assessment:
— subjective sensation of the parturient woman (inaccurate, different threshold of pain
sensitivity);
— palpation;
— external cardiotocography (single-channel and multichannel);
— internal tocography.
2. The cervix of uterus: vaginal examination; ecrvieodilatometry.
3. Descending part: vaginal examination; perineal US.
Treatment. Delivery stimulation therapy with oxytocin, prostaglandins and other
uterotonics at DBA is absolutely contraindicated, otherwise uterine tetanus is possible.
The basic components of DBA treatment.
1. Anticholinergic drugs.
2. Anesthetics (tramal, tramadol, promedol, preparations of morphine type).
3. beta-adrenoceptor agonists (partusisten, intrapartal).
4. Psycotherapy, electroanalgesia, seduxen, relanium, narcosis.
5. Peridural anesthesia.
6. Amniotomy.
7. Cesarean section.
Conditions of administration of uterotonics:
— absence of fetal bladder;
— correspondence of fetal dimensions to the maternal pelvis.
Contraindications:
— clinically and anatomically contracted pelvis;
— operated uterus;
— anomalous positions and presentations of the fetus;
— fetal distress;
— complete placental, presentation;
— premature detachment of the normally and low located placenta;
— vaginal stricture;
— renewed perineal rupture of the 3rd degree;
— dystocia, atresia, scar changes of the neck of uterus;
— hypersensitivity.
Treatment:
— terbutaline in the dose of 250 meg i.v. slowly during 5 min or salbutamol — 10 mg in 1
L of physiologocal liquids for i.v. infusions or Ringer's lactate — 10 drops a min.
Criteria of birth activity character assessment:
A. Tocographically (Table 1):
Table 1. Tocographic Criteria of Birth Activity Assessment
Norm
Labor pains frequency per 10 min
Basal tone, mm of mercury
Labor pains intensity (amplitude), mm Hg
Hypodynamics
<2
<8
<30
Labor pains duration, sec
Irregular rhythm, min
Activity, Montevideo units
<50
3
<100
60-100
1-2
100-250
2-5
8-12
30-50
Hyperdynamics
>5
>12
> 50
> 100
<1
> 250
B. By the cervical dynamics (Table 2):
Table 2. Birth Activity Assessment by Cervical Dynamics
Hypodynamics
Latent phase (duration)
(Smoothing of the uterine cervix, the rate of dilation up to
3—4 cm)
Active phase (duration)
(The rate of dilation from 4 to 8 cm)
Deceleration phase (duration)
>
Norm
7.5 h (5)
Hyperdynamic
s <
0.35 cm/h
>
>
2-3 h (1-1.5)
1.5 cm/h
1.5-2 h (1-1.5)
(The rate of dilation from 8 to 10 cm)
1.0 cm/h) (1.5)
Duration of the 1ststage
>
Note: Figures for multipara women are given in brackets. 18(14)
10-12 h (6-7)
Induction and augmentation of the labor
The culmination of normal pregnancy involves three stages: prelabor, cervical ripening and
labor. These occur as a continuum rather than as isolated events. Endogenous prostaglandins
play a part in all these processes. Interventions to artificially ripen the cervix, induceute
rinecontractions and augment labor onceit is in progress also lack distinct boundaries. This
chapter will briefly discuss reasons for these interventions and methods which may be
used. Labour induction and augmentation may be a source of conflict and distress. For most
health workers they are seen as routine, technical procedures. For many women, they have
emotive connotations, evoking a sense of personal inadequacy and eroded self-esteem. It is
important for health workers to approach the question of labor induction with sensitivity, and
to involve women in the decision-making process. Labor induction is one of the most frequent
medical procedures in pregnant women. It is a major intervention in thenormal courseof
pregnancy, with thepote ntial to set in motion a cascade of interventions,
particularly Caesarean section. However, with modern methods of labour induction, this risk
appears to have diminished.
When should labour be induced? The decision to induce labour is a matter of rather
complex clinical judgement. It usually constitutes a choice between three options: allowing
the pregnancy to continue, inducing labour or performing elective Caesarean section.
The decision takes into account a number of factors.
• Anticipated benefits to the mother, such as improving a medical condition which is
caused or aggravated by pregnancy, including pre-eclampsia, placental abruption and certain
respiratory, hepatic and cardiac disorders; relieving discomfort, such as from multiplepr
egnancy, polyhydramnios or spontaneous symphysiotomy; allowing essential treatment to be
commenced, such as for cervical cancer; relieving emotional distress after intrauterine death;
or alleviating anxiety about the baby’s well-being.
• Estimated risks to the mother, such as increased pain and need for analgesia, uterine
hyperstimulation, Caesarean section, infection, complications of the procedures, post-partum
haemorrhage, uterine rupture (very rarely), anxiety if the induction is protracted or
<
<
<4
unsuccessful, and loss of self-esteem because of perceived failure to givebirth normally. •
Anticipated benefits to the baby, such as improved growth and development when intrauterine
growth is suboptimal, and reduced risk of intrauterine death from complications such as
diabetes, prolonged pregnancy (beyond 41 weeks), amnionitis, prelabour ruptured
membranes, rhesus immunization, fetal compromise and cholestasis of pregnancy.
• Estimated risks to the baby, such as prematurity and compromisefr om uterinehype
rstimulation. Several factors influence the decision.
• The condition of the mother. • The condition of the baby.
• The gestational age of the baby, and level of certainty about the baby’s age. When fetal
lung maturity is uncertain, amniocentesis may be performed to assess markers for lung
maturity such as the alcohol ‘shake’ test, lecithin/sphingomyelin ratio and phosphatidyl
glycerol level.
• The likelihood that induction of labour will be efficient and vaginal delivery
successful. The last factor is in part dependent on the state of the uterine cervix, which is
related to the imminence of spontaneous labour.
The ‘ripeness’ of the uterine cervix The process of softening, shortening and partial
dilation of the cervix usually takes place in the days or weeks prior to the onset of labour, but
thetiming of this process is variable. An unfavourable or ‘unripe’ cervix is one which has
undergoneminimal changeand is morer esistant to attempts at induction of labour. In the first
trimester, 50% of the dry weight of the cervix is tightly aligned collagen, 20% smooth
muscleand
the
rest
is
ground substance
composed
of
elastin
and
glycosaminoglycans (Chondroitin, dermatan sulphate and hyaluronidase). During pregnancy,
hyaluronidase increases from 6 to 33%, whereas dermatan and chondroitin, which bind
collagen more tightly, decrease. Collagenase and elastase enzymes increase, as do the
vascularity and water content. A standardized method of semiquantitative clinical scoring of
the cervix was described by Bishop in 1964, and has since been modified (see Table 3).
Table 3. Modified ‘Bishop’ scale
A score of 6 or more predicts the likelihood of successful induction of labour. A score of 5
or less is regarded as being unfavourablefor induction of labour, and useof artificial ruptureof
theamniotic sac and/or oxytocin infusion are unlikely to be successful. More recently,
measurement of fibronectin in cervicovaginal secretions has been used to predict the
imminence of labour, with variable success.
Methods of induction of labour with a favourable cervix. The more favourable the
cervix the greater the likelihood of efficient labour induction, irrespective of the
method chosen. Artificial rupture of the membranes (amniotomy) using a toothed forceps or
purpose-designed plastic hook, is a simple method of labour induction. Depending on
the urgency of the labour induction, oxytocin infusion may bestarte d with theamniotomy or
may beuse d only if progress after amniotomy is inadequate. Because of the considerable
variability in sensitivity of the myometrium to oxytocin, oxytocin is administered as a variable
dose infusion, titrated against uterine contractions. A typical dosagesche dulewould be1
mU/min, doubling therate of infusion every 20–30 min until adequate uterine contractions are
achieved or a rate of 32 mU/min is reached. Once labour is established theinfusion ratemay
bepr ogressively reduced, as the myometrial sensitivity increases, to a rateof about 7 mU/min.
Amniotomy should beavoide d if thewoman is not known to befr eeof infections such as HIV
and hepatitis, in which case oxytocin infusion may be used with intact membranes. Because
amniotomy and/or oxytocin infusion tend to be ineffective when the cervix is unfavourable,
it is customary to useamniotomy and/or oxytocin infusion for labour induction with
favourable
cervix
and prostaglandins
when
the
cervix
is
unfavourable.
However, prostaglandins may equally be used when the cervix is favourable and in fact
several trials (with rather small numbers) have shown various prostaglandins,
including misoprostol, to bemor ee fficient than oxytocin infusion for labour induction with
favourable cervix and associated with greater satisfaction in the women.
Methods of induction of labour with an unfavourable cervix Themainstay of induction
of labour with an unfavourable cervix is the use of exogenous prostaglandins or methods to
stimulate the release of endogenous prostaglandins to ‘ripen’ the cervix and induce
contractions.
Prostaglandins for labour induction Labour induction with prostaglandin F2 alpha
was introduced in the 1960s. Subsequently, formulations of prostaglandin E2 (PGE2,
dinoprostone) were developed which largely replaced the use of F2 alpha. The most common
routeof administration is vaginal, and tablets, suppositories, gels and pessaries have been
developed. Arandomized comparison found similar effectiveness for a 10-mg PGE2 sustained
release vaginal insert compared with 3 mg PGE2 vaginal tablets twice at a 6-h interval.
In seven out of eight women with uterine hyperstimulation, removal of the vaginal insert was
sufficient to normalizeute rineactivity . In thePGE2 tablet group eight out of nine with uterine
hyperstimulation required medical treatment. A wide variety of dosages and dosing intervals
are in use. A limiting factor for theuseof prostaglandin E2 preparations in many countries has
been the cost. PGE2 tablets (3 mg 6–8 hourly to a maximum doseof 6 mg) are
recommended in preference to PGE2 gel (2 mg for nulliparous women with modified Bishop
cervical score <4, 1 mg for all others, repeated 6 hourly to a maximum dose of 4 mg). In the
case of ruptured membranes, intravenous oxytocin is recommended as an alternative initiating
agent, as detailed in p. The effectiveness of oxytocin is optimized with ruptured membranes. If
oxytocin is used after PGE2, 6 h should elapse after the last vaginal dose of PGE2
to reducetherisk of uterinehype rstimulation.
Intracervical prostaglandins PGE2 may be administered into the cervical canal,
in smaller dosages than those used vaginally, with the objectiveof optimizing thelocal effect
on thece rvix. Administration is somewhat more cumbersome and no clear advantages over
vaginal administration have emerged.
Intravenous oxytocin alone. Traditionally, the use of oxytocin has been accompanied by
amniotomy. In countries with high HIV prevalence, amniotomy is avoided in women not
known to be free of HIV infection. However, oxytocin without amniotomy is significantly less
effective than vaginal PGE2 for labour induction in women with unfavourable cervices.
Amniotomy Rupturing the amniotic membranes through the cervix has been documented
as a method of labour induction for over 200 years. Arise in prostaglandin metabolites with
a relationship to the induction–delivery interval following artificial rupture of membranes has
been demonstrated. This method has theadvantagethat theuseof exogenous uterinestimulants,
with therisk of uterinehype rstimulation, is avoided, and the amniotic fluid may be
observed. However, thepr oceduremay beuncomfortableand it gives rise to the possibility of
ascending infection. Prolonged rupture of the membranes may increase the risk of fetal
infections including HIV, and the procedure itself might place the fetus at increased risk of
HIV if the skin of the presenting part is scratched. With an unfavourable cervix, amniotomy is
often not technically possible.
Intravenous oxytocin with amniotomy The combination of intravenous oxytocin and
amniotomy is commonly used in women with favourable cervices.
Misoprostol Misoprostol, an orally active, stable prostaglandin E1 analogue, has entered
clinical use in Obstetrics and Gynaecology on a wide scale without having been registered
for such use. The American College of Obstetricians and Gynecologists’ Guidelines for
induction of labour recommend that misoprostol 25 μg 3- to 6- hourly is effective for
induction of labour (level A evidence), and 50 μg 6-hourly may be appropriatein
somesituations, though increased risk of complications has been reported (level B evidence).
In most of the dosage regimens used, misoprostol is at least as effective as conventional
methods of labour induction. In doses above 25 μg 4–6-hourly vaginally, misoprostol is
associated with fewer failures to deliver vaginally within 24 h than dinoprostone. The greater
efficiency of misoprostol has been related to more rapid cervical ripening.
Uterine hyperstimulation Systematic review has found vaginal misoprostol in the dosages
used to be associated with more uterine hyperstimulation with non-reassuring fetal heart rate
changes than is PGE2. As misoprostol was also morepote nt as a uterinestimulant in
thesetrials, it is difficult to besur e whether the difference is pharmacological or purely
dose related. MECONIUM-STAINED LIQUOR Meconium-stained liquor is significantly
more common with labour induction with misoprostol than with either vaginal or intracervical
PGE2. Wehavepr eviously postulated that certain myometrial stimulants may cross
the placenta to stimulate fetal bowel smooth muscle and cause meconium passage. However,
misoprostol and dinoprostone have similar stimulatory effects on rat ileum relative to the
myometrial effect. An alternative explanation for the increased meconium passed during
misoprostol induction of labour is that ther esistanceof misoprostol to placental 15hydroxyprostaglandin dehydrogenase enables more misoprostol to enter the fetal circulation
than does PGE2. PRECIPITATE DELIVERY Precipitate delivery (labour < 2 h) has been
described as a complication of misoprostol. Most reviews and trials have not documented the
occurrence of precipitate delivery. In fact ‘mean time to delivery’ is frequently given as a
primary endpoint. Precipitate deliveries may contribute to apparently favourable mean
induction to delivery times, without being identified as an unfavourable outcome.
The importance of precipitate delivery is that it may be a marker for excessive uterine
response to misoprostol and risk of uterine rupture. RUPTURE OF THE UNSCARRED
UTERUS There have been numerous reports of rupture of an unscarred uterus following
misoprostol labour induction, including a maternal death within 7 h of labour induction with
onedoseof misoprostol 50 μg vaginally in a healthy woman with uneffaced cervix. Without a
reliable basis of comparison, it is unclear whether the risk of uterine rupture following
misoprostol induction is greater or less than with other methods of labour induction. WOMEN
WITH PREVIOUS CAESAREAN SECTION Several cases of rupture of uterine scars
following misoprostol induction have been reported. A recent retrospective study found
significantly more cases of uterine rupture or dehiscence following cervical ripening
with misoprostol than when oxytocin or prostaglandin E2 were used. Misoprostol should not
be used in women with uterine scars. CAESAREAN SECTION The relationship between
misoprostol use and Caesarean section is a complex one. The trend in randomized trials has
been an increase in Caesarean sections for fetal heart rate abnormality and a reduction for poor
progress of labour, giving a reduction overall. PERINATAL OUTCOME Despite increases in
uterine hyperstimulation, most reviews and trials have shown no significant difference
in perinatal outcome following misoprostol labour induction versus other methods. POSTPARTUM HAEMORRHAGE Increased post-partum haemorrhage was noted in
a retrospective study of misoprostol induction compared with the general obstetric population
and in a randomized trial following labour induction with vaginal misoprostol 50 μg versus 25
μg 4-hourly (9.8 versus 2.2%). Conclusion: Misoprostol is a highly effective agent for labour
induction. Complications remain a matter of concern, particularly uterine hyperstimulation,
precipitate labour, meconium-stained liquor, uterine rupture and postpartum haemorrhage.
The available data suggest that risks can beminimize d with theuseof small dosages and
that the starting dose should not exceed 25 μg vaginally or orally. Limited evidence favours
the oral over the vaginal route. There is a need for large-scale randomized trials comparing
low-dose misoprostol regimens with conventional methods to determine with more certainty
the relative rates of rare adverse outcomes.
Augmentation of labour Spontaneous labour is divided into a latent phase of variable
duration and an active phaseduring which rapid dilation of the cervix takes place. The active
phaseon average commences when the cervix is 3 cm dilated and fully effaced.
Augmentation of the latent phase of labour The latent phase of labour may be difficult to
diagnose prospectively as late pregnancy painful contractions with all the appearances of true
labour at times fail to progress to activelabour . Thede cision to augment thelate nt phase
of labour, therefore, is more similar to that for labour induction than for augmentation of the
active phase of labour. The same attempts to balance potential benefits and risks should be
applied, also taking into account the distress caused by ongoing uncertainty as to whether
labour is or is not commencing. The latent phase of labour is usually augmented by
amniotomy followed by oxytocin infusion either simultaneously or if the response to
amniotomy alone is inadequate. For women not known to be free of HIV infection, oxytocin
alone or prostaglandins may be used as for labour induction. Extra-amniotic saline
infusion may be used if the cervix is narrow enough to retain the Foley catheter bulb.
Augmentation of the active phase of labour The activephaseof labour may be augmented
routinely, as in the ‘active management of labour’ introduced by O’Driscoll and co-workers in
the 1960s or selectively when labour progress is considered to be inadequate
and thecausethought to beinade quateute rinee fficiency. The active management of labour
involved stringent criteria for thediagnosis of labour, amniotomy, oxytocin infusion and a
commitment to the labouring woman of one-to-one presence of a memberof the health-care
team, and an expedited delivery. Subsequent research has sought to isolate the individual
effects of these interventions. Routine amniotomy is associated with reduced labour duration
(on average1–2 h), useof oxytocin and low 5-min Apgar scores and a trend to increased
Caesarean section. The Cochrane systematic review of continuous support for women during
labour and birth found a reduction in use of analgesia, operative delivery and
dissatisfaction with the experience of childbirth, and a non-significant reduction in labour
duration. Continuous support is recommended for all women during labour. The essential
factor in the use of augmentation to treat poor progress in labour is the diagnosis of ineffective
uterine activity. Acommon problem is to distinguish between prolonged latent phase of labour
and poor progress in the active phase. This may be reduced by stringency in the diagnosis of
theactivephase . Progress in theactivephase of labour is best monitored with a graphical
representation of cervical dilation and descent of the presenting part against
time(thepartograph). Various modifications of the partograph havecomeinto use. Typically,
labour progress is considered inadequate when cervical dilation is delayed by 2 or 4 h beyond
the expected rate (1 cm/h). If there is no evidence of fetopelvic disproportion uterine
activity is assumed to be inadequate and the labour augmented. In the event of uncertainty
intrauterine pressure may be monitored to assess uterine activity objectively.
Contractions occurring every 3 min, lasting 45 s, and reaching intrauterine pressures of 60–80
mmHg are considered optimal. External assessment of uterine contractions by palpation or
with indirect tocography is useful for monitoring the duration and frequency of contractions,
but not theinte nsity. Labour augmentation for women with previous Caesarean section is
controversial. For breech presentation, poor progress in theactivephaseof labour is regarded as
a possible indicator of fetopelvic disproportion and Caesarean section recommended rather
than labour augmentation. When labour augmentation is decided upon, the usual method used
is amniotomy (once HIV infection has been excluded) with or without oxytocin infusion as
outlined in p. for labour induction.
Conclusion The most important consideration with respect to labour induction is nothow,
but whether labour induction should be undertaken. Careful consideration must be given
to potential benefits and risks to mother and baby, both physical and emotional, as well as to
thestateof theute rine cervix. When the cervix is unfavourable, oxytocin infusion and/or
artificial rupture of the membranes are less likely to be effective in inducing labour. PGE2
administered vaginally in various formulations is theusual method of labour induction.
Misoprostol is a less expensive method. At dosages around 25 μg 4-hourly vaginally, both
effectiveness and side effects appear similar to PGE2. Oral misoprostol may have advantages
over the vaginal route of administration. Mechanical methods of labour induction stimulate
the cervix and lower uterine segment to release endogenous prostaglandinsSeveral other
methods of labour induction have not been adequately assessed by randomized trials to be
able to be advocated for general use.
Tests and Assignments for Self — assessment.
Multiple Choice.
Choose the correct answer / statement:
1. If there has been no descent of the presenting part for over 1 hour during the second
stage of labor, this would be classified as:
A - Prolonged latent phase; B - Protraction disorder; C — Arrest disorder; D - Normal
labor.
2. Which of the following provides a quantitative measurement of the strength of uterine
contractions?
A - Manual palpation of maternal abdomen;
B - Intrauterine pressure catheter;
C - "Indentation" of uterus on palpation during contraction;
D - Tocodynamometer.
3. The hypotonic uterine dysfunction may be managed by:
A - Rest; B - Augmentation with oxytocin; C - Amniotomy; D - All of above.
4. All of the following are risks to the fetus from prolonged labor Except:
A - Sepsis;
B - subdural hematoma;
C - Cerebral damage;
D - Hemorrhage.
Real - life situations to be solved:
5. A 20-year-old primapara at 41 week's gestational age presents complaining of uterine
contractions for ten hours. Her uterine contractions are occurring every 8-10 minutes "during
25-30 seconds and judged to b mild in intensity. Fetal heart rate is 130 per minute. Pelvic
examination shows the cervix to be completely effaced and 1.5 cm dilated and membrane-;
intact. What is the diagnose and the treatment?
III. Answers to the Self- Assessment.
1. C. 2. B. 3. D. 4. D. 5. First in-term labor, cervical stage of the labor. Primary inertia of
uterine contractions. Management: Artificial rupture membranes is performed with following
augmentation of labor by oxytocin.
Students must know:
1. Etiology and pathotogenes of uterine dysfunctions.
2. The signs of uterine dysfunctions.
3. Treatment of uterine dysfunctions.
4.
Principles of dispensary care of pregnant women with abnormalities of uterine
contractions.
Student should be able:
1. To take history and conduct the obstetric examination.
2. To evaluate the character of uterine contractions and results of additional methods of
examination.
3. To diagnose and differentiate with other types of uterine dysfunction.
4. Prescribe treatment of uterine dysfunction.
5. Work out the preventing methods of uterine dysfunctions.
References:
1. Danforth's Obstetrics and gynaecology. - Seventh edition.- 1994. - P. 545- 550|
2. Obstetrics and gynaecology. Williams & Wilkins Waverly Company. - Thin Edition.1998. -P. 107-115.
3. Basic Gynecoiogy and Obstetrics. - Norman F. Gant, F. Gary Cunningham. 1993. - P.
356-361.
4. Obstetrics.Edited by Prof. I. Ventskivska. – Kyiv. – 2008. – P. 205- 208.