Description of first stage of labour
The progress of labour has been divided into stages and phases, labour is subdivided into four stages they are as follows:
- First stage of labour
- Second stage of labour
- Third stage of labour
- Fourth stage of labour
FIRST STAGE OF LABOUR
This begins with the onset of true labour and ends when the cervix is completely dilated at 10cm.
This stage is subdivided into three phases as follows:
- Latent phase
- Active phase
- Transition phase
Latent phase
This begins with onset of irregular Uterine contraction, the cervix begins to dilate and efface little or with no fetal descent. The cervix dilates from 0 – 4 cm, it lasts for 6 – 8 hours in primip gravida and shortens in multigravida.
The cervical canal shortened from 2 – 5 cm to less than 0.5cm. Uterine contraction becomes established during this phase and increases in frequency, duration and intensity
Active phase
This is characterized by rapid cervical dilatation, initially when two phases of the first stage were recognized. Active phase begins from 4 cm dilation to 10 cm. The cervix dilated 1 cm per hour, fetus descent is progressive, contraction occurs at a frequency of 2-5 times in 10 minutes.
Moderate to strong uterine contractions lasting for 2- 40 seconds progressing to greater than 40 – 60 second s. The woman’s anxiety increases as contraction and pain increases, she may adopt various coping mechanisms
Transition phase
This is from 8 cm dilation to 10 cm, this is the last part of the first stage and the woman demonstrates significant anxiety.
The contractions becomes more intense and forcefully, the woman becomes restless and frequency changing positions, the contractions are strong about 3 – 5 times in10 minutes lasting for 60- 90 seconds as dilatation approaches 10 cm, there is an increase in rectal pressure and uncontrollable urge to bear down, increase in bloody show, spontaneous rupture of membrane, if membrane has not been ruptured already.
There is a sensation of great pressure at the pick of contraction that it seems that her abdomen will burst open.
Physiology of the first stage of labour
The events of first stage of labour are divided into two major categories for better understanding, and they include:
The duration of labour
This varies depending on numerous factors such as parity, birth interval, psychological state, presentation and position of the fetus, maternal pelvis shape and size, and the nature of Uterine contraction. First stage of labour takes the greater part of the labour, especially the latent phase.
Active phase of labour is expected to be completed between 6 – 12 hours, labour last longer in primip gravida woman than multiparous woman, duration of labour should not last longer than 18 hours
Note: World Health Organization (WHO) recommended management of the active phase of labour with pantographs, this will help manage the progress of labour and action to be taken if labour is prolonged.
Uterine Action
Series of event occurs in the Uterus during labour such as
- Fundal dominance: This means that contraction starts from the fundus at the corneal and radiates across and downwards the uterus. The contraction is almost more intensity at the fundus but the pick is reached simultaneously over the entire uterus, this enables dilatation of the cervix and expulsion of the fetus
- Polarity: This is a neuromuscular harmony that takes place between the two poles (segments of the uterus) throughout labour. The upper poles contracts strongly and retracts to expel the fetus while the lower Uterine segment dilates to allow the passage of the fetus. If there is disorganization of this harmony, there will be delay in progress of labour
- Contraction and retraction: The uterine muscle has the ability to retain some of the contractions during labour instead of being completely relaxed. This is term retraction. This helps to reduce the cavity thereby expelling the fetus.
- Formation of the upper hand lower uterine segment: towards the end of the pregnancy, the uterus divided into two parts ( the upper and lower segments). The upper segment is the fundus and the body of the uterus while the lower segment is form by the Isthmus and the cervix and is about 8 – 10 cm in length. The longitudinal fibres in the upper segments pull up the lower segment
- Formation of retraction ring: There is development of a ridge known as retraction ring between the upper and lower segments. This is due to contraction of the upper Uterine segment and the dilatation and distension of lower segment. In an obstructed labour, physiologic retraction ring becomes visible at the symphysis pubis term the bandl’s ring
- Show: as the cervix begins to dilate the operculum which forms during pregnancy breaks and releases, this is noticed by the woman as blood stain mucus discharge at onset of labour, the bloody discharge is just a stain from the capillary of parietal decidual as the chorion attached at the end of first stage of labour during the transitional period, there is an appearance of fresh red blood that is signify second stage of labour. This is also referred as show
- Cervical effacement: This is taking up of cervical canal to the lower uterine segment, this means that the longitudinal muscle fibres that attaches to the internal os is pulled upward
- Cervical dilatation: This occurs as a result of the uterine action and counter pressure applied by the intact membrane and the presenting part.