ONSET OF LABOUR

 (1) Uterine distension:-

Uterine stretching of Myometrium

Gap junction protein

Receptors for Oxytocin & specific contraction

Onset of labour

(2) Feto-placental circulation:-

Activation of fetal hypothalamic pituitary adrenal axis

Increase CRH (Corticotrophin Releasing harmones)

Increase ACTH (Release of ACTH)

Fetal adrenals

Cartisol secretion

Production of Oestrogon & Prostaglandins

From the placenta

Onset of labour 

(3) Oestrogen:-

Oestrogen

Increase Synthesis Promotes the Increase Release of Oxytion

of prostaglandins     Synthesis of myometrial      from maternal pituitary

(PGF2)             receptor of oxytocin & Onset of labour

Onset of labour         Prostaglandins

                Onset of labour

(4) Progesterone:-

Decrease Level of progesterone before onset of labour

Alteration in the estrogen: Progesterone ratio

Increase Prostaglandin synthesis

Onset of labour

(5) Prostaglandins:-

Prostaglandins are Imp factor which imitate and maintain labour

Sites of synthesis of prostaglandins

Amnion chorion, decidual cell & myometrium

Note:- Prostaglandins synthesis reaches a peak during the birth of placenta contributing to IHS expulsion and control PPH

Labour Pain:-

(1) True Labour pain:- Painful uterine contraction

Intensity duration

Show blood mixed c cervical mucus

Progressive effacement & dilatation of cervix

(2) False Labour pain:- Pain in dull in nature 

Irregular

No effacement & dilation of cervix

Abnormal Labour (Dystocia):- Any deviation from the normal labour is called abnormal labour or Dystocia

Terms:-

Labour staste on the expected date – 4% cases

On the week Less or More than EDD- 50% cases

2 week earlier 11 week later – 30% cases

At 42 weeks – 10% cases

> 43 weeks – 4% cases

Oxytocin and Myometrium Oxytocin Receptors:-

Large no of oxytocin receptors are present in the fundus compared to lower segment and the cervix

Receptor no increase during Pregnancy reaching maximum during labour.

Receptor sensitivity increase during labour

Oxytocin stimulates synthesis and release of PGs

Pre- Labour:-

In myometrium oxytocin receptors increase changes are

(1) Lightening:- (Welcome sign) in fundal height seen at term which brings sense of belief to the mother.

(2) Cervical ripening:- Softening of the cervix less than 1.5 cm in length admit a finger easily and is dilate

(3) False labour pain

(4) Show- Expulsion of cervical mucus plug mixed with blood is called ‘Show”

(5) Formation of “bag of water during uterine contraction 

After the contraction pass off, the bulging may disappear completely.

This is almost a certain sign of onset of labour.