Normal labour

Definition

A series of events that take place in the genital organs in an effort to expel the products of conception out of the womb through the vagina into the outer world is called labour.

Dutta D C (2004)

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Normal Labour or Eutocia

• Labour is called normal if it fulfils the following criteria:

→ spontaneous in onset and at term→ with vertex presentation→ without undue prolongation→ natural termination with minimal

aids→ without having any complications

affecting the health of the mother and /or the baby 3

Date and onset of labour

unpredictable, varies to case to case.Naegeles ’s formula - a rough guide. According to the formula labour starts:According to the formula labour starts:Approximately on the expected date in 4%, One week on either side in 50%2 weeks earlier and 1 week later in 80%, at 42 weeks in 10% and at 43 weeks plus in 4%

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The essential forces of labour

Passageway

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Passenger

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Powers

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Psyche

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Physiology

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Psychology of the mother

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Preparation by the mother

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Position

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Professional providers

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Place of birth

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Procedures

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People

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Politics : Social context

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Pressure interface

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Causes of onset of labour1.Uterine distension: Stretching effect of the

myometrium by the growing fetus and liquor amnii can result in prostaglandin release.

2.Feto placental contribution: Prior to onset of labour – activation of fetal hypothalamic pituitary adrenal axis- increased CRH – increased release of ACTH – fetal adrenals – increased cortisol secretion – accelerated production of estrogen and prostaglandins from the placenta.

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3. Estrogen:- Increases the release of oxytocin from maternal pituitary.- Promotes the synthesis of receptors for oxytocin in the myometrium

and decidua.- Accelerate lysosomal disintegration in amnion cells – resulting in

increased prostaglandin synthesis.- Stimulates the synthesis of myometrial contractile protein through

cAMP.- Increases the excitability of the myometrial cell membranes.

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4. Progesterone: Alteration in the estrogen : progesterone ratio – prostaglandin synthesis

5. Prostaglandins: Prostaglandins are the important factors which initiate labour.

- It activate the myometrial contractile system- Major site of synthesis of prostaglandins are – amnion, chorion,

decidual cells and myometrium.- Synthesis is triggered by – rise in estrogen level, glucocorticoids,

mechanical stretching in late pregnancy, increase in cytokines, infection, vaginal examination, ROM

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6. Oxytocin:- There is oxytocin receptors in the uterus- Oxytocin receptors are increased in the uterus with the onset of

labour - Oxytocin promotes the release prostaglandins from the decidua - Oxytocin synthesis is increased in the decidua & in the placenta- Vaginal examination and amniotomy cause rise in maternal plasma

oxytocin level.

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7. Neurological Factor: nerve pathways and adrenergic receptors are present in myometruim- Oestrogen acts on receptors- Pregesterone acts on the receptors

8. Contractile system of myometrium- Actin- Myosin- Adenosine tryphosphate- Enzyme myosine light chain kinase- Ca ++ 23

True labour pain False labour pain

Pain more often felt in front of the abdomen or radiating towards the thigh.

Dull in nature, and usually confined to the lower abdomen.

Intermittent powerful uterine contractions with hardening of the uterus.

Continuous uterine contraction and unrelated with hardening of the uterus

Presence of 'show' Absence of 'show’

Progressive effacement &dilatation of the cervix

Cervical effacement & dilatations are absent

Formation of the "bag of waters" There is no formation of "bag of waters“

Pain is not relieved by enema or administration sedatives.

Usually relieved by enema and administration of a sedative. 24