Labour is the process by which the baby, placenta, amniotic sac and fluid are expelled. It is unique and varies from woman to woman, or from one labour to the next for the same woman. In true labour, the uterus contracts causing the muscle fibres to shorten and thicken. This causes the cervix, or opening of the uterus, to thin out and dilate.
Dilation refers to the opening of the cervix. The cervix is fully dilated at 10 cm.
Effacement is the thinning out and shortening of the cervix and is measured from 0% (long and thick) to 100% (completely thinned out), or the length of the cervix may be described in centimetres.
The station is a term used to describe the position of the baby’s head in relation to the pelvis. The progress of labour is also monitored by the descent of the head.
The doctor or midwife measures these factors with an internal vaginal examination to monitor the progress of labour.
Labour is divided into four stages:
• First stage from the onset to complete effacement and dilation of the cervix.
• Second stage begins with complete dilation and ends with the birth of the baby.
• Third stage is the delivery of the placenta.
• Fourth stage is the first hour after birth or recovery period.
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