Abnormal Uterine Action: Definition, Causes and Types

Abnormal Uterine Action

Definition:

This is an upset in the normal uterine action – lac k of polarity.

Causes:

i.                  Mostly unknown

ii.                  Predisposing factors;

iii.                  Psychological influence – fear

iv.                  Disproportion and malpresentation/Malposition e.g. Breech, occipito posterior position.

v.                  Parity: there is always more resistance in first pregnancy – Primigravida and lasity in the uterine muscle tones in multiparous women can also give rise to poor neuro-muscular reflex.

vi.                  Age: Common in elderly primigravidae than in young primips.

vii.                  Maturity of the pregnancy: Failure in the formation of the lower uterine segment.

viii.                  Uterine over-distension as in Twins and polyhydrammios .

Types:

1. Hypotonic Uterine Action – Uterine Inertia

This term is used when the uterine contractions are weak, short lived (duration), infrequent, irregular and shallow. The contractions are less painful and the uterus is well relaxed between contractions. The labour may begin with this type of contraction and continue throughout the stage of labour. This is known as “primary uterine inertia”. Usually common with the primigravidae. It is a faint shadow of normal pattern of labour – so called “False labour.” It has less effect on cervical dilatation . It leads to prolonged labour, but becomes stronger in the second stage of labour.

The condition may develop during labour when the contractions start well but later become weak, irregular and infrequent. This is known as “secondary uterine ine rtia” it is basically uterine exhaustion or uterine fatique. It may occur in first or second stage of labour. Usually follows excessive uterine action. Common in impending rupture of uterus e.g. disproportion. (Is a nature’s way of preventing uterine obstruction or rupture).

In the third state: It is characterized by flabby and inexcitable state of the uterus. It gives rise to delay in the separation of placenta or post partum haemorrhage from partial placental separation and a failure of uterine contraction.

Management:

1.           Admission

2.           Exlude CPD

3.           ARM, Syntocinon-small dose 2.5 unit in 450mls at 15 drops per minute.

4.           Correct electrolyte imbalance or loss.

5.           Prevent dehydration.

6.           Monitor maternal and fetal conditions (Prevent acidosis).

7.           Fetal blood sampling (P.H) if necessary. 

8.           C/S or forceps/vacuum in 2^nd stage of labour.

9.           Antibiotic – if membranes have ruptured up to 12hrs .

Nursing Care

1.           Reassure the patient

2.           Observation of: Vital sign.

Contraction – Frequency, strength & duration. Effec t on descent of the presenting part.

3.           Vaginal examination, Liquor amni – colour, amount &  odour.

4.           Accurate fluid balance chart. Urinalysis

5.           Light diet.

2. Hypertonic Uterine Action

This term is used when there is persistent high tone of uterine contractions during and in between contractions. Contractions are usually frequent strong without relaxation and usually very painful with sudden effect on cervical dilatation. So it may give rise to erratic uterine contraction leading to precipitate labour. Cervical and perineal tear may occur. Fetal hypoxia may occur, injuries to the baby’s head. Umbilical cord may tear or cult leading to haemorrhage .

Management

·              Exclude CPD,

·              Small dose of oxytocin – 5 unit/litre – To correctthe rhythm of contractions.

·              Relief of pain – sedation, Narcotic e.g. valium 10m g, pethidine100mg /Pethilorfan 2ml.

·              Correct dehydration and dectrolyte inbalance – i.v.  infusion.

·              C/S if no progress in cervical dilatation in 4-6hrs – forceps/vacuum in 2^nd stage.

·              Frequent vaginal examination review.

·              Early admission with subsequent deliveries.

·              General nursing care in labour

Observation of vital signs, contractions, urinalysis.

Provide comfort

Maintain input and output chart.

3. Incoordinate uterine action

This occurs as a result of lack of polarity (Neuro muscular disharmony) between the upper and the low pole of the uterus. The contractions are irregular in term of strength. There is an increase muscle tone in the lower uterine segment, in some cases even between contractions. This increases the intral uterine pressure. So

patient experiences pains or discomfort more than the strength of contraction and it lasts longer.

There may be a reversal of the uterine action, when the lower segment is contracting strongly and pains are felt at the back and lower abdomen. The patient feels pains at the onset, in between and at the termination of the contractions. It may not be effective thereby leading to prolonged labour. The cervical dilatation may be very slow; cervical may be very thick, tight and unyielding. The uterus is tender to touch. There may be early rupture of membranes and signs of maternal or fetal distress or both.

4. Construction Ring

A localized spasm of a ring of circular muscle fibres of the uterus. This occurs between the two poles at the isthmus. Rare, less than 1-1000. It usually forms around a narrow part of the fetus (neck) preventing descent but occasionally at the level of the internal OS. It is a physiological ring but exaggeration of it is known as BANDL’S RING.

IT may occur in any stage of labour, when it occurs in 3^rd stage it is known as hour glass contraction.

Causes:

·              Hypertonic uterine Action

·              Early rupture of membranes

·              Interference – Use of oxytocin or manipulation unde r light or no anaesthesia – Internal version.

Diagnosis

·              No advancement of the presenting part.

·              Tenderness of the upper uterine segment to touch – Action is meeting with obstruction.

·              Could be felt on palpation.

Treatment

·              Anaesthesia: before attempting delivery

·              Sedation – To calm patient and relief pains (but no effect on the contriction ring).

·              10mls of 20% solution of magnesium sulphate i.v. (Epsom salt).

·              Amyl Nitrite 1 ample to inhale – vasodilator – to r elieve the muscle spasm.

5. Cervical Dystocia

This is a condition when there is slow or no dilatation of the cervix even in the presence of good uterine contractions. It may result from cervical stenosis as a result of previous cervical tear or infection, amputation, irradiation or cauterization (cervical erosion).

Diagnosis:

On vaginal Examination:

·              Cervix feels thin, tight, rigid and unyielding first then later becomes thick and oedematous.

·              There may be caput on the presenting part.

·              Labour is marked with severe back ache.

Treatment:

·              Sedation,

·              C/S

Nursing care:

Same as hypertonic uterine Action.