Normal labour is labour that starts spontaneously without stimulation of the uterus in any way, without any operative interference and resulting in the delivery of a fetus of a viable age. Labour presents with regular, painful and forceful uterine contractions (more than one every ten minutes) , resulting in descent of the presenting part and dilatation and effacement of the cervix.

 

What is false labour (Braxton Hicks contractions)?

This refers to irregular weak uterine contractions which may occur before term or at term. They are usually not painful. Braxton Hicks contractions can cause a lot of anxiety and may even lead to premature admission to the labour ward.

 

How can I differentiate a false labour from a true labour?

The only definitive way to differentiate a false labour from a true labour is to get a vaginal examination (V/E) done by a midwife or a doctor. The vaginal examination will reveal  a dilated cervix and or effaced cervix.

In true labour there must be more than one contraction in 10 minutes. Contractions can either be recorded by modern instruments or by feeling the abdomen with the palm of the hand.False labour is usually not very painful and not forceful.

It must be emphasized that labour does not begin at a point, it is a gradual physiological transition from late pregnancy to labour.

 

What causes the onset of labour?

The mechanism responsible for the onset of labour is still not properly understood.

 

What is known is that prostaglandin hormones are primarily responsible for stimulating uterine contractions of labour . It is believed that prostaglandin action on the uterus is mainly due to cervical ripening rather than stimulating uterine contractions. Cytokines, oxytocin ,steroid hormones, endothelin-1 and platelet activating factor (PAF) may stimulate prostaglandin synthesis ,while progesterone and phospholipase A2 inhibitors may inhibit prostaglandin synthesis.

 

A fall in plasma progesterone has also been observed prior to the onset of labour. Even though oxytocin stimulates uterine contractions , its concentration in the blood does not rise near term. Relaxin, is another hormone that is thought to help cervical ripening.

 

Prostaglandins and oxytocin may increase intracellular free calcium ions which in turn causes contractions by formation of the contractile entity of  actin-phosphorylated myosin.

 

Uterine contractions are involuntary in nature . There is little or no neuronal control over uterine contractions.

 

The duration of pregnancy is also affected by the fetal genotype.

 

There is progressive shortening of the uterine smooth muscles as labour progresses .This is called retraction . Retraction mainly takes place in the upper segment of the uterus. After contractions they do not return to their original size. This enables the lower segment to become thinner and more stretched, eventually the cervix also becomes stretched and taken up into the lower segment of the uterus.

 

References:

Dewhurst’s Textbook of Obstetrics and Gynaecology for Postgraduates (Sixth Edition)-Edited by Keith Edmonds FRCOG , FRACOG

Oxford Handbook of Clinical Specialties-6 th edition

Obstetrics by Ten Teachers- edited by Stuart Campbell and Ash Monga- 17th edition

Textbook of Obstetrics and Gynaecology for Medical Students by Akin Agboola et al-2nd edition

 

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