PHYSIOLOGY OF FIRST SOL

It entails the following:

• Duration
• Cervical effacement
• Cervical dilatation
• Uterine action
• Mechanical factors

Duration:

The length of first SOL varies widely and is influenced by parity, birth interval, psychological state, presentation and position of the fetus, maternal pelvic shape and size, and the character of the uterine contraction. By far, the greatest part of labor is taken up by the first stage and it is common to expect the active phase to be completed within 6-12 hours. We expect the cervical dilatation to be 1 cm per hour. A cervical dilatation rate of 0.5 cm per hour is also within the parameters of normal.

Cervical Effacement:

This refers to the inclusion {taking up} of the cervical canal into the lower uterine segment. It is believed that this process takes place from above downwards, meaning that the muscle fibers surrounding the internal OS are drawn upwards by the retracted upper segment and the cervix merges into the lower uterine segment.

The cervical canal widens at the level of the internal OS, whereas the state of the external OS remains unchanged. It normally occurs when labor begins. In nulliparous women, dilatation does not occur till effacement is complete while in multiparous women, both effacement and dilatation occur simultaneously and a small canal may be felt in early labor, referred to as “multiparous OS”.

Cervical Dilatation:

This is the process of enlargement of the os uteri from a tightly closed aperture to an opening large enough to permit passage of the fetus. It is assessed in “centimeters” and full dilatation at term equates to about 10 cm. It is as a result of uterine action and the counter-pressure applied by either the intact bag of membranes or the presenting part, or both, and also a well flexed fetal head.

Pressure applied evenly to the cervix causes the uterine fundus to respond by contraction and retraction, often referred to as the “Ferguson reflex”.

Uterine Action:

• Fundal Dominance: All contractions commence in the fundus and spread downwards. Here the contraction lasts longest, more intense, but the peak is reached simultaneously over the whole uterus and the contraction fades from all parts together.
• Polarity: This refers to the neuromuscular harmony that prevails between the two poles or segments of the uterus throughout labor. The two poles act harmoniously during each uterine contraction. The upper pole contracts strongly and retracts to expel the fetus; the lower pole contracts slightly and dilates to allow expulsion to take place.
• Contraction and Retraction: The contraction does not entirely pass off during labour, as the muscle fibers retain some of the shortening of contraction instead of becoming completely relaxed {retraction}. It assists in the progressive expulsion of the fetus, such that the upper segment of the uterus becomes gradually shorter and thicker and its cavity diminishes.

Intensity and Resting Tone:

Generally before labor becomes established, uterine contractions may occur every 15-20 minutes, lasting for about 30 sec. The contractions usually occur with rhythmic regularity and the intervals between them where the muscles relaxes {resting tone} gradually lessen while the length and strength gradually intensifies through the latent and into the active phase of the first SOL.

By the end of the first stage, the contractions may occur at 2-3 minute intervals, last for 50-60 sec and are very powerful.

Formation of the Upper and Lower Uterine Segments:

By the end of pregnancy, the body of the uterus is described as having divided into two segments which are anatomically distinct.

These are the upper and lower uterine segments. The upper segment having been formed from the body of the fundus, is mainly concerned with contraction and retraction, and is thick and muscular. The lower one is formed of the isthmus and the cervix, and is about 8-10 cm in length and is prepared for distension and dilatation.

The Retraction Ring:

This is a ridge which develops between the upper and lower uterine segments. The physiological retraction ring gradually rises as the upper segments contracts and retracts and the lower segment thins out to accommodate the descending fetus. It rises no further when the cervix is fully dilated and the fetus can be expelled out.

However in extreme cases of mechanically obstructed labor, this physiological retraction ring becomes visible above symphysis pubis and is described as “Bandl’s ring” which may consequently be associated with fetal compromise.

Show:

As a result of the dilation of the cervix, the operculum, which formed the cervical plug during pregnancy is released.

The woman may observe a blood stained mucoid discharge a few hours before, or within a few hours after labor commences from the ruptured capillaries in the parietal decidua where the chorion has become detached from the dilating cervix and should only be staining.

Mechanical Factors:

• Formation of hind and fore waters
• General fluid pressure
• Rupture of membranes
• Fetal axis pressure

NURSING CARE OF WOMEN IN FIRST STAGE OF LABOUR

General:

• Clean and safe environment use aseptic techniques
• Constant observation
• Communication/emotional support

Routine Care for a Mother in First Stage of Labour

After admission of the mother in first stage of labour, the midwife performs the following:

Emotional Support and Respect: The midwife must gain the mother’s confidence and cooperation in order to eliminate anxiety. Talk to her to keep her informed often on the progress and what is happening.

Positioning: The mother is allowed to adopt the position in which she feels more comfortable. Bending in back, sitting in low chair or bed leaning forward help in engagement.

Upright and walking helps in fetal descent. Lateral facilitate kidney function and promote blood circulation to the fetus.

Ambulation: In early labour the mother is encouraged to walk around if the membranes have not ruptured and if they are found ruptured, the mother is confined to bed to reduce on the risk of cord prolapse. Infection prevention measures must be observed for example, the mothers personal hygiene, and vaginal examination must be done under precaution.

Care of the Bladder: Encourage the mother to pass urine frequently at least every two hours to allow the presenting part to descend and prevent delay in labour.

If the mother is unable to pass urine AND bladder is found full as suprapubic bulging, catheterize.

Nutrition: Labour requires a lot of energy and the stomach is slow to empty during labour. Oral fluids are encouraged to mothers during labour. It can also be supplemented by intravenous infusion.

Relief of Pain: This can be achieved through the following measures:

• • Rubbing the back
  • Walking around
  • Allowing the mother to adopt the position in which she may be comfortable
  • Warm bath and counselling
  • Encourage positive breathing techniques

Provide Comfort and Assistance:

• • Assist in daily care
  • Praise and reassure her
  • Give detail of progress of labor

Monitoring:

• • Monitoring maternal physiological changes, vital signs, urinary output
  • Monitoring of foetal well being
  • Proper recording