MINISTRY OF PUBLIC HEALTH OF UKRAINE
NATIONAL PIROGOV MEMORIAL MEDICAL UNIVERSITY, VINNYTSYA
CHAIR OF OBSTETRICS AND GYNECOLOGY №1
Methodological instruction for practical class for foreign students
Uterine birth activity anomalies
MODULE 2: Obstetrics and gynecology
CONTEXT MODULE 9: Pathology of pregnancy, labor and puerperium
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 betaadrenoceptor 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 long-term 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
Labor pains frequency per 10 min
Basal tone, mm of mercury
Labor pains intensity (amplitude), mm
HgLabor pains duration, sec
Irregular rhythm, min
Activity, Montevideo units
Hypo-
Norm
Hyper-
dynamics
<2
<8
<30
2-5
8-12
30-50
dynamics
>5
>12
> 50
<50
3
<100
60-100
1-2
100-250
> 100
<1
> 250
B. By the cervical dynamics (Table 2):
Table 2. Birth Activity Assessment by Cervical Dynamics
HypoLatent phase (duration)
Norm
Hyper-
dynamics
>
7.5 h (5)
dynami
<
cs
(Smoothing of the uterine cervix, the rate of
0.35 cm/h
dilation up to 3—4 cm)
Active phase (duration)
(The rate of dilation from 4 to 8 cm)
>
2-3 h (1-1.5)
1.5 cm/h
<
Deceleration phase (duration)
>
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
>
10-12 h (6-7)
Note: Figures for multipara women are given in brackets.
18(14)
Induction and augmentation of the labor
<4
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 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 nonreassuring 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
15-hydroxyprostaglandin
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
SECTION Several
cases
of
WITH
rupture
PREVIOUS
of
uterine
CAESAREAN
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. POST-PARTUM
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. Extraamniotic 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 4hourly 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 laborl 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. 545550|
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.