ABNORMAL UTERINE ACTION
Normal labour is characterized by coordinated uterine contractions associated with progressive dilatation of the cervix and descent of the fetal head. Normal labour is associated with cervical dilatation ≥ 1cm \ hour in a nulliparous woman and is likely to end in successfully vaginal delivery. Overall labour abnormalities occur in about 25% of the nulliparous women and 10% of multiparous women. Improved labour management can reduce the number of dystocia due to abnormal uterine action.
CERVICAL DILATATION IN NORMAL LABOUR
During labour, the cervix opens wider to allow the baby to pass through. By definition cervical dilatation is the opening of the cervix.
Dilation refers to how big the opening of the cervix is and is measured from 0 (closed cervix) to 10 (fully opened cervix).
Dilatation of cervix usually takes place as follows in each phases of labour
· Latent phase: 0-3 centimeters
· Active Labor: 4-7 centimeters
· Transition: 8-10 centimeters
· Complete: 10 centimeters. Delivery of the infant takes place shortly after this stage is reached (although the mother does not always push right away.)
In primigravida mothers, the cervix may be fully effaced, feeling like a paper although not dilated enough to admit a finger tip. It is usually measured with fingers and recorded in centimeters. 1 finger 2 finger, 3 finger or fully dilated.
One finger associates to 1.6 cms.
How cervix dilates
In multipara mothers, In the later stages of pregnancy (ie in prelabour phase), the cervix may already have opened up to 1-3 cm (or more in rarer circumstances), But during labor, repeated uterine contractions lead to further widening of the cervix to about 6 centimeters. From that point, pressure from the presenting part (head in vertex births or bottom in breech births), along with uterine contractions, will dilate the cervix to 10 centimeters, which is "complete."
Friedman (1954) ) ploted cervical dilatation and decent of the fetal head against duration of labour in hours. Cervical dilatation follows a sigmoid curve. In the active phase of labour, dilatation has
• acceleration phase,
• phase of maximum slope, and
• the phase of deceleration.
The latent phase in primigravida mothers is often long as 8 hours during which the effacement occur.
Average cervical dilatation in primigravida mothers is 0.35 cms in latent phase. In multi latent phase is short and dilatation occurs simultaneously.
During the active phase of labour, in primigravida dilatation occur at a rate of 1 cm per hour and in multigravida mothers, it occurs at the rate of 1.5 cm per hour beyond 3 cm dilatation.
Cervical dilatation in the phases of the graph are as follows
• acceleration phase is 2.5 – 4 cms
• phase of maximum slope – 4-9 cms
• phase of deceleration – 9-10 cms
DEFINITION OF ABNORMAL UTERINE ACTION
Any deviation of the normal pattern of uterine contractions affecting the course of labour is designated as disordered or abnormal uterine action.
Abnormal uterine action
Normal polarity Abnormal polarity
( inco- ordinate uterine action)
Excessive uterine inertia Spastic Colicky Asymmetry Constriction Generalized Cervical
Contraction ( common) lower uterus uterine ring tonic dystocia
Segment contraction contraction
Obstruction (-) Obstruction (+)
Precipitate labour tonic uterine contraction
and retraction ( Bandl’s ring)
over active uterus Ineffective uterine contraction
As the physiology of normal uterine contraction is not fully understood, the cause of its disordered action remains obscure. However , the following clinical conditions are often associated:
· Prevalent in first birth specially with advancing age of the mother
· Prolonged pregnancy
· Over distension of the uterus due to twins and or hydramnios
· Psychologic factor
· Contracted pelvis, malpresentation and deflexed head. All these lead to ill fitting of the presenting part into the lower uterine segment. This probably results in inhibition of the local reflex which is needed to produce effective contraction of the upper segment.
· Full bladder and loaded rectum reflexly inhibit uterine contraction
· Injudicious administration of sedatives, analgesics and oxytocics
· Premature attempt at vaginal delivery or attempted instrumental vaginal delivery under light anaesthesia.
Uterine inertia is the common type of disordered uterine contraction but is comparatively less serious. It may complicate any stage of labour. It may be present from the beginning of labour or may develop subsequently after a variable period of effective contractions.
Uterine contraction: the intensity is diminished; duration is shortened; good relaxation in between contractions and the intervals are increased. General pattern of uterine contractions of labour is maintained but intrauterine pressure during contraction hardly rises above 25mm Hg.
1. Patient feels less pain and discomfort during uterine contraction
2. Hand placed over the uterus during uterine contraction not only reveals hardening of the uterus before the patient feels pain but the contraction also outlasts the pain.
3. Uterine wall is easily indentable at the acme of a pain.
4. Uterus becomes relaxed after the contraction; fetal parts are well palpable and fetal hearts rate remains good.
5. Internal examination reveals;
· Poor dilatation of the cervix
· Membranes usually remain intact
· Cervix well applied to the presenting part
· Associated presence of contracted pelvis, malposition, deflexed head or malpresentation may be evident.
EFFECT ON THE MOTHER AND FETUS:
Maternal exhaustion is unusual and appears late. The fetal distress is rare specially with intact membranes.
Careful evaluation of the case is to be done:
o To be sure that the patient is in true labour
o To exclude cephalopelvic disproportion or malpresentation
o To plan out the management protocol
Detected in first stage:
Place of caesarean section:
· Presence of contracted pelvis
· Evidences of fetal or maternal distress
Contemplating vaginal delivery:
· To keep up the morale of the patient
· To empty the bowel by enema and bladder by encouraging the patient to empty at intervals, failing which catheterization is to be done
· To maintain nourishment by infusion of 5% dextrose
· Adequate sedation is ensured by intramuscular Pethidine 100 mg or combination of Pethidine 75 mg and Sparine 50 mg
Acceleration of uterine contraction can be brought about by low rupture of the membranes followed by Oxytocin drip if not contraindicated. An infusion of 1 unit of Oxytocin dissolved in 500ml 5% dextrose is started. The drip rate should be slow at first and is to be gradually increased until effective contractions are set up. Close watch of the maternal and fetal conditions and nature of uterine contractions is mandatory. The drip is to be continued till 1 hour after delivery; if, however, cervical dilatation remains unsatisfactory and \ or fetal distress appears, Caesarean section is the best alternative.
Detected in second stage
If the case is first seen at this stage, careful evaluation of the case is to be done to exclude contracted pelvis, malpresentation and to determine station of the head in relation to ischial spines and fetal condition.
Place of caesarean section
In presence of contracted pelvis or malpresentation where vaginal delivery is found unsafe and fetal condition remains good, caesarean section may be preferred even at this stage.
1. Head low down – Forceps or ventouse delivery
2. Head not sufficiently low down
· Stimulation of uterine contraction by oxytocin drip or
· Ventouse extraction. Difficult forceps should be avoided
3. Craniotomy – If the baby is dead
Active management of the third stage is advocated
Progressive cervical dilatation needs an effective stretching force by the presenting part. Failure of cervical dilatation may be due to :
a. Ineffective uterine contractions
b. Malpresentation, Malposition (abnormal relationship between the cervix and the presenting part)
c. Spasm (contractions) of the cervix
Cervical dystocia may be primary or secondary
PRIMARY CERVICAL DYSTOCIA
Commonly observed during the first birth where the external os fails to dilate. Uterine contractions are often ineffective. On occasion, edema of the anterior lip may occur and delivery may be accomplished with avulsion of the anterior lip or by annular detachment of the cervix.
In presence of associated complications (malpresentations and malposition) caesarean section is preferred.
If the head is sufficiently low down with only thin rim of cervix left behind, the rim may be pushed up manually during contractions or tractions is given by ventouse. In others where the cervix is very much thinned out but only half dilated. Duhrssen’s incision at 2 and 10’o clock positions followed by forceps or ventouse extraction is quite safe and effective.
SECONDARY CERVICAL DYSTOCIA
This type of cervical dystocia results usually due to excess scarring or rigidity of the cervix from the effect of previous operation or disease.
GENERALIZED TONIC CONTRACTION (UTERINE TETANY)
In this condition pronounces retraction occurs involving whole of the uterus upto the level of internal os. Thus there is no physiological differentiation of the active upper segment and the passive lower segment of the uterus. As there is no thinning of the lower segment, there is no chance of rupture of the uterus. The uterine contraction ceases and the whole uterus undergoes a sort of tonic muscular spasm holding the fetus inside (active retention of the fetus)
1. Failure to overcome the obstruction by powerful contractions of the uterus
2. Injudicious administration of oxytocics
The patient is in prolonged labor having severe and continuous pain. Abdominal examination revels the uterus to be somewhat smaller in size, tense and tender. Fetal parts are neither well defined, nor is the fetal heart sound audible. Vaginal examination reveals jammed head with big caput; dry and oedematous vagina.
o Correction of dehydration and keto acidosis: by rapid infusion of Ringer’s solution
o Antibiotics : To control infection
o Adequate pain relief
Induced by oxycocis can be managed by tocolytics (terbutalin 0.25mg S.C) Oxytocin infusion should be stopped.
Is done in majority of the cases specially when obstruction is suspected. Destructive operation is an option when the fetus is dead.
A labour is called precipitate when the combined duration of the first and second stage is less than two hours. It is common in multiparae and may be repetitive. Rapid expulsion is due to the combined effect of hyper active uterine contractions associated with diminished soft tissue resistance. Labour is short as the rate of cervical dilation is 5 cm/hour or more for the nulliparous women.
Extensive laceration of the cervix, vagina and perineum (to the extent of complete perineal tear)
PPH due to uterine hypotonia that develops subsequently
Amniotic fluid embolism
Intracranial stress and haemorrhage because of rapid expulsion without time for moulding of the head.
The baby may sustain serious injuries if delivery occurs in standing position.
Bleeding from the torn cord and direct hit on the skull are real hazards.
The patient having previous history of precipitate labour should be hospitalized before labour. During labour, the uterine contractions may be suppressed by administering ether or magnesium sulphate during contractions. Delivery of the head should be controlled. Episiotomy should be done liberally. Elective induction of labour by low rupture of membranes and careful conduction of controlled delivery may be advantageous. Oxytocin augmentation should be avoided.
TONIC UTERINE CONTRACTION AND RETRACTION ( BANDL’S RING)
This type of uterine contraction is predominantly due to obstructed labour.
PATHOLOGIC ANATOMY OF THE UTERUS
There is a gradual increase in intensity, duration and frequency of uterine contraction. The relaxation phase becomes less and less; ultimately a state of tonic contraction develops. Retraction, however continues. The lower segment already thinned by circumferential dilatation in the first stage, elongates and becomes progressively thinner to accommodate the fetus driven from the upper segment.
A circular groove encircling the uterus is formed between the active upper segment and the distended lower segment , called pathological retraction ring ( Bandl’s ring) . Due to pronounced retraction, the placental site is also affected and there is marked reduction of blood flow to the intervillous space leading to fetal jeoparady or even death.
In primigravidae, further retraction ceases in response to obstruction and labour comes to a stand still- a state of uterine exhaustion. Contractions may recommence after a brief period of rest with renewed vigour.
In multiparae, retraction continues with progressive circumferential dilatation and thinning of the lower segment. There is progressive rise of the Bandl’s ring ;moving nearer and nearer to the umbilicus and ultimately the lower segment ruptures.
1. Patient is in agony from continuous pain and discomfort and becomes restless.
2. Features of exhaustion and keto – acidosis are evident
3. Abdominal palpation reveals;
· Upper segment is hard, uniformly convex and tender. Lower segment is distended and tender.
· The pathological retraction ring is placed obliquely between the umbilicus and symphysis pubis and rises upwards in course of time.
· Taut tender round ligaments may be felt on either side. This is because, the uterine attachments of the round ligaments have been raised by the shortening of the upper segment and distension of the lower segment.
· Fetal parts may not be well defined
· FHS is usually absent
4. Internal examination reveals:
· Vagina- dry and hot and the discharge is offensive
· Cervix fully dilated
· Membranes are absent
· Cause of obstructed labour is revealed
It is a preventable condition. The abnormality, either in the passage ( bony or soft tissue) or in the passenger ( malpresentation or malformation of the fetus) can be detected during antenatal or early intranatal period and appropriate treatment solves the problem
· Morphine 15 mg is given intramuscularly
· 5% dextrose drip is started
· Ampicillin 500 mg intramuscularly is given
· Keto – acidosis is to be promptly and effectively corrected prior to definite treatment by infusion of 5% dextrose and Ringer’s solution.
Ø To rule out the presence of rupture uterus
Ø To relieve the obstruction with minimal hazard to the mother. Fetus is either dead or in moribund state. Frantic attempts at delivering a moribund baby by any method ignoring the risk involved to the mother, should not be contemplated.
· There is no place of internal version
· Routine uterine exploration after vaginal delivery is to be done to exclude rupture uterus
· Caesarean section is rarely indicated.
DIFFERENCE BETWEEN CONSTRICTION RING AND RETRACTION RING
It is a manifestation of localised inco-ordinated uterine contraction.
It is an end result of tonic uterine contraction and retraction
Undue irritability of the uterus.
Following obstructed labour
Usually at the junction of upper and lower segment but may occur in other places. The position does not alter.
At the junction of upper and lower segment. The position progressively moves upwards
Upper segment contracts and retracts with relaxation in between lower segment remains thick and loose.
Upper segment is tonically contracted with no relaxation
The wall becomes thicker, lower segment becomes distended and thinned out
Almost unaffected unless the labour is prolonged
Maternal exhaustion, sepsis appear early
oUterus feels normal and not tender
oFetal parts are easily felt
oIon Ring is not felt
oRound ligament is not felt
oFHS is usually felt
o Uterus is tense and tender
o Not easily felt
o Ring is felt as a groove placed obliquely
o Usually absent
o The lower segment is not pressed by the presenting part
o Ring is felt usually above the head
o Features of obstructed labour are absent
o Lower segment is very much pressed by the forcibly driven presenting part
o Ring cannot be felt vaginally
o Features are present
o Maternal exhaustion is a late feature
o Fetal anoxia usually appear late
o Chance of uterine rupture is absent
o Maternal exhaustion and sepsis appear early
o Fetal anoxia and even death are usually early
o Rupture uterus in multi gravidae is common
Principle of treatment
To relax the ring followed by delivery of the baby or to cut the ring during C.S
To relieve the obstruction by safe procedure after excluding rupture uterus.
1. Some psychologic factors in prolonged labor due to inefficient uterine action
The role of psychological factors as causative or contributory to the development of ineffective uterine activity during labor is reviewed.
Eighteen primiparas with inefficient uterine action, i.e., no progress in dilatation or effacement of the cervix in the absence of cephalopelvic disproportion, were compared to 43 primiparas with normal labor from the same
Obstetrical and psychological findings in the two groups were compared. The mean duration of labor was 23.9 hours in the abnormal group and 10.8 hours in the control group. Significant statistical differences were found between the mean scores of the two groups in the following items: attitude to motherhood; attitude to sex and marriage; relationship to mother; adjustment to pregnancy; concept of early home life; predelivery concept of labor; habitual neurotic bodily complaints; habitual anxieties, worries and fears; attitude to first menses; and attitude to father of child. The difference between the mean total scores of these ten items was highly significant in distinguishing the women who had had ineffective uterine activity during labor from the control group.
2. Relaxin deficiency in the placenta as possible cause of cervical dystocia. A case report. Entenmann AH, Seeger H, Voelter W, Lippert T
Department of Obstetrics and Gynecology, University of Tübingen, F.R.G.
In a case of cervical dystocia which had to be delivered by caesarean section, the placenta was examined for relaxin content. The placenta was processed by acidic acetone extraction and separation of the raw extract on a carboxymethylcellulose column. The activity of relaxin was estimated by means of heterologous porcine radioimmunoassay. The elution profile of the placenta extract showed significant differences to that of the placenta in normal deliveries i.e. there was no evidence of typical protein peaks with relaxin activity. It is suggested that there is possibly a causal relationship between the lack of placental relaxin and the pathological behaviour of the cervix during delivery
3. The experience of precipitate labor
Health Sciences Centre Site, Faculty of Nursing, University of Manitoba, Winnipeg, Canada.
BACKGROUND: Despite abundant research on psychosocial factors related to childbirth, no studies have focused on the specific phenomenon of a precipitate labor. A descriptive exploratory study was conducted to investigate this experience. METHOD: Semistructured interviews were conducted in 1992 with 11 women 3 to 4 months after they gave birth. Transcribed interviews were then analyzed using latent content analysis. RESULTS: The experience of precipitate labor was categorized in terms of physical experience (perception of labor length and contractions), psychological experience (relationship of how women perceived birth to their prenatal expectations, and emotional trajectory of disbelief, alarm panic, and relief), and external factors (support persons and hospital system). CONCLUSIONS: Understanding the experience of precipitate labor is essential before caregivers can offer appropriate support to clients. Perinatal caregivers gain valuable insight into a woman's experience by comprehending the speed, intensity, and emotional impact specific to precipitate labor.
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