Presentation on Labor

NORMAL LABOUR

DEFINITION
Labour is the process by which the uterus empties its contents after the 28th week of pregnancy. It involves the contraction and retraction of uterine muscle fibres, the dilatation of the cervical Os and the expulsion of the baby, liquor amnii, placenta and membranes. Labour can be described as spurious, true, normal or abnormal.
Spurious labour sometimes called false labour is characterized by erratic, irregular uterine contractions, which could be painful. It occurs before the onset of labour and causing the woman to think that labour has started. The contraction appear stronger when the woman is in bed and weaker when she is up and about. The contractions do not bring about effacement and dilatation of the cervix. It is important to note that the contractions are quite real but it’s not into a rhythmic pattern. The pain and the discomfort that the woman experiences are not false.
True labour is characterized by uncomfortable contractions, which are slight at first but increasing in severity and frequency. They occur at regular intervals and the cervix dilates as a result of the contractions.
Normal labour is that which starts spontaneously at term with fetus presenting by vertex and the process is accomplished within 24 hours by unaided maternal effort without any serious injury to the mother and baby.
Abnormal labour is any labour that does not follow the normal process of normal labour.
CAUSES OF ONSET OF LABOUR
What initiates labour is not known but many explanations have been proffered. Some of the explanations include:
Labour starts at term because of the overstretching and over distension of the uterus. This explains why patients with multiple pregnancy or conditions where there is over distension of the uterus, e.g. polyhydramnios tend to go into premature labour.
The placental efficiency is diminished towards term, resulting in reductions in the level of oestrogen and progesterone. The uterus becomes sensitive to the effect of oxytocin from the posterior pituitary gland and the mother goes into labour.
There is an increased contractility of the uterus towards term. The Braxton Hick’s contractions increase in amplitude and may bring about onset of labour.
Hyperpyrexia, cyanosis and emotional upset have been linked with onset of labour.
PREMONITORY SIGNS OF LABOUR
Premonitory signs of labour are signs and symptoms that predict the approach of labour. They are very useful when the gestational age of a pregnancy is not definitive. They include:
A drop in fundal height occurs and the uterus looks almost pendulous as the fetus sinks into the lower uterine segment. This allows the mother to breathe more easily because the fundus uteri no longer cause elevation of the diaphragm and diminution of the area occupied by the lungs. This sign is referred to as lightening and may occur two weeks before term.
Frequent micturition occurs because the fetal head presses on the bladder which is closely related to the lower uterine segment.
Braxton Hick’s contractions become more intensified and the mother becomes conscious of them. She experience backache or pain on walking due to relaxation of the pelvic joints. The Braxton Hick’s contractions and backache could make the patient erroneously believe that she is in labour.
The cervix is soft, almost effaced and the cervical Os admits one or two finger tips. The pelvic floor and perineal muscles are relaxed.
Most mothers tend to lose weight towards the end of pregnancy. This is believed to be as a result of the reduction in the amount of liquor amnii at term.
THE COURSE OF LABOUR
Normal labour occurs between 37 and 42 weeks gestation. The WHO defines normal labour as low risk throughout, spontaneous in onset, with the foetus presenting by the vertex, culminating in the mother and infant in good condition following birth. Once physiological labour commences, its progress is measured by the descent of the head and the dilatation of the cervix. Although labour is a continuous process, it is divided into three stages for the purpose of description, (first, second and third stages of labour).
The course of labour is influenced by the following factors:
Muscular activity of the uterus, the diaphragm, thoracic and abdominal muscles.
The size, shape and resistance of the birth canal including the bony pelvis, cervix uteri, vagina and the pelvic floor.
The size, lie and presentation of the fetus as well as the placenta and membranes.
The general health of the mother and her fortitude.
If these factors are favourable and the mother has confidence in her midwife and doctor, the progress of labour should be normal and the process should be accomplished within 24 hours. Anxiety can increase the production of adrenaline which inhibits uterine activity and may in turn prolong labour. The attitude of the midwife and advice and guidance she gives during pregnancy influence the progress of labour and the attitude of partners to each other and to their baby after birth.

Reference:
https://www.gfmer.ch/Obstetrics_simplified/normal_labour.htm
https://www.ncbi.nlm.nih.gov › pmc
ABC of labour care: Physiology and management of normal labour