the powers in normal labour1

• Presented by :Presented by : Asmaa Beltagy. 194Asmaa Beltagy. 194

•Supervised by:Supervised by:Prof.dr.Hossam Ibrahim Azab.Prof.dr.Hossam Ibrahim Azab.

Objectives What are forces of normal labour?

Uterine contraction: Anatomical and physiologic

considerations Uterine contractions throughout

pregnancy and labour Methods of assesment of uterine

contractions Effects of uterine contractions

Bearing down efforts Abnormalities of uterine contractions

I-Uterine contractions• The uterine musculature during pregnancy is arranged in

three strata:

The uterus in pregnancy is functionally divided into:

• Physiological retraction ring:• a ridge around the inside of the uterus that forms at

the junction of the thinned lower uterine segment and thickened upper segment.

• Pathological Retraction Ring (Bandl’s ring)• It is a retraction ring during obstructed labour due to

marked retraction and thickening of the upper uterine segment while the lower segment is markedly stretched and thinned.

Physiological properties of uterine contractions:1. Contraction: It is temporary shortening of muscle fibres.

2. Retraction: It is permanent shortening of muscle fibres contractions and retractions contribute to:• a. Taking up (effacement) of the cervix.• b. Reduction of uterine volume and

Expulsion of the fetus. 3. Progressive: increase in intensity and

frequency with time.4. Effective.

5. co-ordination• The pace-maker: The uterine pace-maker lies just

anterior to the uterotubal-junction i.e. at the uterine cornu

• Polarity • Triple descending gradient• Fundal-dominance

Important definitions:1. Rest tone: in between uterine contractions (6-12 mmHg).

2. Amplitude: The amount of rise of the intra-uterine pressure caused by the

contractions:1st stage – 40-60 mm Hg2nd stage – 80 mm Hg

3. Frequency of contractions: The number of contractions/unit of time (10 minutes).

4. Uterine activity:measured by Montevideo units.= Intensity X frequency over 10 minutes period. Inadequate uterine contractions, defined as less than 180

Montevideo unitsOr Alexandria units= montivideo units × mean duration of each

contraction.

Uterine activity throughout pregnancy and labour

• 1. In early pregnancy:

felt by P/V Palmer's sign.

• 2. Braxton Hicks Contractions: also known as practice contractions, are sporadic Painless uterine contractions that are Felt abdominally from 16 weeks up to 36 weeks:

• False labour pains • infrequent, • occur after 36 weeks,• irregular • Of short duration.• Highest amplitude 10-15 mmHg.• Respond to analgesics.• No effect on the cervix.• No bulging of the membranes.• increasing in intensity and

frequency and becoming more rhythmic

• true labour pains :• Painful contractions:

Abdominal-Pain : Backache:

• Regular

• Don`t respond to analgesics

• Increased amplitude up to 60 mmHg.

• Frequency: 2-4/10 minutes.

• Progressive dilatation and effacement of the cervix.

• Membranes are bulging during contractions.

False labour pains True labour pains Less painful More Painful

infrequent More Frequent.

increases after 36 weeks

irregular Regular

.

Amplitude less than 10-15 mmHg Increased amplitude up to 60 mmHg.

Respond to analgesics Don`t respond to analgesics

No effect on the cervix. Progressive dilatation and effacement of the cervix.

No bulging of the membranes. Membranes are bulging during contractions.

Methods of assessment of uterine contractions:

1. Manual palpation.

2. External tocodynometry.

3. Internal manometry (intra-uterine catheter).

Effects of uterine contractions• A) Descent of the fetus:• 1- Before ROM: Generalised intraamniotic

pressure:

• 2- After ROM :Direct fetal axis pressure:

• B) Cervical effacement: contractions and retraction of the uterinelongtudinal fibers and dilatation

• The dilatation of the cervix is the result of two factors:

• active: retraction of the longitudinal fibers of the uterus.

• Passive: the downward push of the bag of water

• C) Expulsion of the placenta

• D) Control of bleeding from placental site :

II-Bearing down efforts• When to start ? • At the end of first stage

(onset of second stage) after full cervical-dilatation. Must be simultaneous with uterine contractions.

• When to stop?• With crowning of fetal

head

• Contraindicated in:

PRECIPITATE LABOUR

• Definition A labour lasting less than 3 hours.

• Aetiology It is more common in multiparas with:

• strong uterine contractions, • small sized baby,  • roomy pelvis, • minimal soft tissue resistance.

HYPOTONIC UTERINE INERTIA

• Definition

The uterine contractions are infrequent, weak and of short duration.

• Types

• Primary inertia• Secondary inertia

• Aetiology

• the following factors may be incriminated:• Primigravida particularly elderly.• Anaemia and asthenia.• Nervous and emotional as anxiety and fear.• Overdistension of the uterus.• Myomas of the uterus interfering mechanically

with contractions.• Malpresentations, malpositions and

cephalopelvic disproportion. • Full bladder and rectum.

HYPERTONIC UTERINE INERTIA (Uncoordinated Uterine Action) The condition is more common in

primigravidae and characterised by: • Prolonged labour.• Uterine contractions are irregular

and more painful. • High resting intrauterine pressure in

between uterine contractions• Slow cervical dilatation. • Foetal and maternal distress.

CONSTRICTION (CONTRACTION) RING

• It is a persistent localised annular spasm of the circular uterine muscles.

• at any part of the uterus but usually at junction of the upper and lower uterine segments.

• occur at the 1st, 2nd or 3 rd stage of labour.

Thank you:)