The Powers

 

The forces acting to expel the fetus and placenta are derived from three sources:

1.      Involuntary uterine contractions

2.      Voluntary bearing-down efforts

3.      Contraction of the levator ani muscles

Uterine Contractions

Uterine contractions (primary powers) are involuntary. This is attested

Description of Uterine Contraction

In describing a uterine contraction, reference is made to the following characteristics:

1.      Frequency

Contractions occur intermittently thought labour. They begin at about 20 to 30 minutes apart and become closer together until, at the height of the expulsion efforts, they are as frequent as every 2 to 3 minutes.

2.      Regularity

Contractions occur more and more regularly as labor becomes well established.

3.      Duration

The length of time a contraction lasts increases from 30 seconds to between 60 and 90seconds

4.      Intensity

The strength of the contraction also increases as labour progresses, from weak contractions noted in labour to strong expulsive contractions (intrauterine pressure measured at 50 to 75 mmHg) evidenced near the time of delivery.

Each contraction exhibits a wavelike pattern; it begins with a slower increment gradually reaches an acme, and then diminishes rather rapidly (decrement). Next there is an interval of rest (intrauterine pressure is 8 to 15 mmHg), which is broken when the next contraction begins.

Contractions that have been augmented by administration of oxytocin tend to increase more rapidly. Women describe them as sharper, harder, and more uncomfortable contractions.

Assessment of uterine contraction

 

There are three methods of assessing contractions.

·1    The first is the subjective description given by the woman;

·2    the second, palpation and timing by a nurse or physician; and

·3    the third, use of electronic monitoring devices.

When the woman reports that contractions have begun, she is asked

·4    When did they start?

·5    How often are they coming?

·6    Are they coming regularly?

·7    Would you say they are weak or strong?

Depending on the woman’s knowledge, her answers can be definite or vague, but they serve as a basis for deciding whether she should be admitted to the hospital.

The second method is used routinely throughout labour by the attending nurse.

Palpations are done by using the fingertips, not the palmar surface, and the fingers must be kept moving.

The uterus begins to contract in fundus portion, and as the contraction proceeds, the uterus is less easily indented; at the height of the contraction, the uterus feels very firm or even hard. Then as the contraction diminishes, the fingers can again indent the uterine surface

External monitoring devices measure the frequency and duration of the contractions.

Internal monitoring  measure these factors and also the strength of contractions. The findings are automatically recorded by the machine

 

Voluntray bearing-down efforts

 

As soon as the presenting part reaches the pelvic floor, the woman experiences an urge to push, a voluntray bearing-down efforts (secondary power).

The bearing-down efforts is similar to that used in the process of defecation. However, a different set of muscles is used; the parturient contracts her diaphragm and abdominal muscles and push out the contents of the birth canal.

Bearing-down results in increased intraabdominal pressure. The pressure compresses the uterus on all sides and adds to the power of the expulsive forces.

Implications for Nursing Care

 

This bearing-down reflex must be held in check until full cervical dilation (10 cm). If this disregarded,

·8    the cervix can be bruised and

·9    traumatized as it is forced against the symphysis pubis during pushing.

·10The result may be cervical edema can act to delay cervical dilatation and predisposes the cervix to laceration.

However, the woman can control the urge to push by taking panting breaths similar to blowing out candles.

 

Psychologic response

Woman who are relaxed, knowledgeable of actively participating in the control of the birth process usually experience shorter, less intense labors.

 

Techniques for Assessment

 

Provisional determination of fatal presentation, position and descent may be made by the following techniques:

1.      External palpation after the sixth month of pregnancy

2.      Identification of the location of the maximal intensity of the fetal heart rate (FHR) through auscultation

3.      Vaginal examination

Certain confirmation of fetal presentation or position and the maternal pelvis is possible with the following

1.      Conventional x-ray films (radiographic pelvimetry), which are not recommended because of danger to the fetus, fetal gonads, and maternal gonads

2.      Ultrasonography

 

Abdominal Palpation

 

Use of the four maneuvers of Leopold provides a systematic examination. Proficiency in determining presentation and position by abdominal palpation requires considerable  practice, and thus every learning opportunity must be utilized.

Gross maternal obesity, excessive amniotic fluid (hydramnios), or tumors may make it hard to feel the fetal contours.

Abdominal palpation is done as follows:

·1    The woman empties her bladder before the examination is begun and

·2    lies on her back with one pillow under her head and her knees slightly flexed.

·        The examiner stands facing the woman on her right.

·        The examiner keeps the following assessment in mind while carrying out the procedure:

1.      Is there one fetus or more than one?

2.      What is the presentation (lie)?

3.      What is the position?

4.      Is the presenting part  engaged?

5.      Is there fetal movement?

6.      Do the uterine size and fundal height correspond with the due date (expected date of confinement [EDC])?

7.      Is there any indication of uterine, pelvic or fetal abnormality?

Leopold’s maneuvers are as follows:

1.      The fetal part that occupies the fundus of the uterus is identified first. The fetal head feel round, firm, freely movable, and palpable by ballottement; the breech feels less regular and softer

2.      The back is then identified by using the palmar surface of the hand to note a smooth convex contour anteriorly or to one side. The fetal ventral (front) surface is concave and soft, and the small parts (feet, hands, elbows) are irregularities felt on the side opposite the back

3.      The examiner should next determine with the right hand which fetal part is presenting over the inlet to the true pelvis. This is done by gently grasping the lower pole of the uterus between the thumb and fingers and pressing in slightly.

·        If the fetus is at term, the rounded head presents, and

·        if it is not engaged, it may be rocked gently from side to side

If the presenting part is not engaged, the next step is to determine the attitude of the head.

·        If the cephalic prominence is found on the same side as the small part, the head must be flexed: this is a vertex presentation.

·        If the cephalic prominence is on the same side as the back, the presenting head is extended

·        If the presenting part has entered the pelvis, the maneuver also determines whether or not the presenting part is fixed in the pelvis (engaged).

4.      Finally, the degree of descent is estimated. To do this, the examiner faces the woman’s feet and uses both hands. When the presenting part has descended deeply, only a small portion of it may be outlined.

 

Auscultation

 

The area of maximal intensity of the FHR (i.e., the location of the maternal abdomen where the FHR sounds loudest is an aid in determining the fetal position. For example, in vertex and breech presentation, FHRs are best heard through the back of the fetus. In face presentation, however, FHRs generally are loudest when transmitted through the fetal chest

In vertex presentations FHRs commonly are heard below the mother’s umbilicus in a lower quadrant of the abdomen, but in breech presentation they are heard above the level of the umbilicus.

 

Vaginal examination

 

The examination must be done

·        Carefully,

·        Gently, and

·        Under aseptic conditions.

·        Sterile gloves are used, as well as an aseptic solution.

·        The index and middle fingers are introduced into the vagina.

Discomfort is less if the examining fingers are directed with the palmar surface downward so that the initial pressure is directed toward the less sensitive posterior vaginal wall. Then the fingers may be rotated Assessment consists of answering the following questions:

1.      Is the cervix soft or firm?

·        What is the degree of effacement and dilatation of the cervical os?

2.      Are the membranes intact?

·        If so, are they bulging through the cervical os?

3.      What is the presentation: vertex, breech, or other (e.g., hand, face)?

4.      What is the position?

·        If the vertex presents, the sagittal suture is located and traced to the posterior frontal (Triangle shaped) if the head is well flexed or

·        to the anterior fontanel (diamond shaped) if the head is extended.

·        Once the fontanel is located, its position must be determined in relation to the quadrants of the mother’s pelvis.

·        The most common position is the left occiput anterior (LOA) (i.e., the fetal occiput (O) is located on the mother left (L) and anterior (A) or front part of her pelvis

5.      What is the station?

6.      How well is the presenting part applied against the cervix?

To accomplish the foregoing assessment, the nurse must understand the following terms in addition to those related to presentation and position

 

Effacement of the cervix

 

Effacement of the cervix means the shortening and thinning of the cervix during the first stage of labour.

The cervix, normally 2 to 3 cm in length and about 1 cm thick, is obliterated or “taken up” by a shortening of the uterine muscle bundles during the thinning of the lower uterine segment in advancing labour.

Eventually only a thin edge of the cervix can be palpated when effacement is complete.

Effacement generally is advanced in primigravidas at term before more than slight dilatation occurs.

In multiparas, effacement and dilatation of the cervix tend to progress together.

Degree of effacement is expressed in percentage (e.g., a cervix that is 50 % effaced).

 

Dilatation of the cervix

 

Dilatation of the cervix is widening of the cervix os and the cervical canal during the first stage of labour. The diameter increases from perhaps less than 1 cm to approximately 0 cm to allow delivery of a term fetus. When the cervix is fully dilated , it can no longer be palpated.

Dilatation of the cervix is involuntary and occurs by the drawing upward of the musculofibrous components of the cervix with strong uterine contractions. Pressure exerted by the amniotic fluid while the membranes are intact or force applied by the presenting part also encourages cervical dilatation. Scarring of the cervix as a result of infection or surgery may retard cervical dilatation.

 

Station

 

Progress in the descent of the presenting part is determined by vaginal examination until the presenting part can be seen at the introitus.