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When you have completed this skills chapter you should be able to:
A vaginal examination in labour is a sterile procedure if the membranes have ruptured or are going to be ruptured during the examination. Therefore, a sterile tray is needed. The basic necessities are:
An ordinary surgical glove can be used and the woman does not need to be swabbed if the membranes have not ruptured yet and are not going to be ruptured during the examination.
A vaginal examination in labour is a systematic examination, and the following should be assessed:
Always examine the abdominal before performing a vaginal examination in labour.
An abdominal examination should always be done before a vaginal examination.
This examination is particularly important when the woman is first admitted:
When you examine the cervix you should observe:
The cervix becomes progressively shorter in early labour. The length of the cervix is measured by assessing the length of the endocervical canal. This is the distance between the internal os and the external os on digital examination. The endocervical canal of an uneffaced cervix is approximately 3 cm long, but when the cervix is fully effaced there will be no endocervical canal, only a ring of thin cervix. The length of the cervix is measured in centimetres. In the past the term ‘cervical effacement’ was used and this was measured as a percentage.
Dilatation must be assessed in centimetres, and is best measured by comparing the degree of separation of the fingers on vaginal examination, with the set of circles in the labour ward. In assessing the dilatation of the cervix, it is easy to make two mistakes:
Figure 3B-1: The correct method of measuring cervical dilatation
Rupture of the membranes may be obvious if there is liquor draining. However, one should always feel for the presence of membranes overlying the presenting part. If the presenting part is high, it is usually quite easy to feel intact membranes. It may be difficult to feel them if the presenting part is well applied to the cervix. In this case, one should wait for a contraction, when some liquor often comes in front of the presenting part, allowing the membranes to be felt. Sometimes the umbilical cord can be felt in front of the presenting part (a cord presentation).
If the membranes are intact, the following two questions should be asked:
The presence of meconium may change the management of the patient as it indicates that fetal distress has been and may still be present.
An abdominal examination must have been done before the vaginal examination to determine the lie of the fetus and the presenting part. If the presenting part is the fetal head, the number of fifths palpable above the pelvic brim must first be determined.
When palpating the presenting part on vaginal examination, there are four important questions that you must ask yourself:
The presenting part is usually the head but may be the breech, the arm, or the shoulder.
Features of an occiput presentation. The posterior fontanelle is normally felt. It is a small triangular space. In contrast, the anterior fontanelle is diamond shaped. If the head is well flexed, the anterior fontanelle will not be felt. If the anterior fontanelle can be easily felt, the head is deflexed.
Figure 3B-2: Features of an occiput presentation
Figure 3B-3: Features of a face presentation
Features of a brow presentation. The presenting part is high. The anterior fontanelle felt is on one side of the pelvis, the root of the nose on the other side, and the orbital ridges may be felt laterally. If the presenting part is not the head, it could be either a breech or a shoulder.
Figure 3B-4: Features of a brow presentation
Figure 3B-5: Features of a breech presentation
Position means the relationship of a fixed point on the presenting part (i.e. the point of reference or the denominator) to the mother’s pelvis. The position is determined on vaginal examination.
The point of reference (or denominator) is:
For example, if the posterior fontanelle (i.e. the fetal occiput) in a vertex presentation points upwards (anterior) and towards the mother’s left side the position of the presenting part is called a left occipito-anterior position.
Figure 3B-6: Examples of the position of the presenting part with the patient lying on her back
Descent and engagement of the head is assessed on abdominal and not on vaginal examination.
Moulding is the overlapping of the fetal skull bones at a suture which may occur during labour due to the head being compressed as it passes through the pelvis of the mother.
In a cephalic (head) presentation, moulding is diagnosed by feeling overlapping of the sagittal suture of the skull on vaginal examination, and assessing whether or not the overlap can be reduced (corrected) by pressing gently with the examining finger.
The presence of caput succedaneum can also be felt as a soft, boggy swelling, which may make it difficult to identify the presenting part of the fetal head clearly. With severe caput the sutures may be impossible to feel.
The sagittal suture is palpated and the relationship or closeness of the two adjacent parietal bones assessed. The amount of moulding recorded on the partogram should be the most severe degree found in any of the sutures palpated.
The degree of moulding is assessed according to the following scale:
0 = Normal separation of the bones with open sutures.
1+ = Bones touching each other.
2+ = Bones overlapping, but can be separated with gentle digital pressure.
3+ = Bones overlapping, but cannot be separated with gentle digital pressure.
3+ is regarded as severe moulding.
When assessing the pelvis on vaginal examination, the size and shape of the pelvic inlet, the mid-pelvis and the pelvic outlet must be determined.
It is important to use a step-by-step method to assess the pelvis.
Start with the sacral promontory and follow the curve of the sacrum down the midline.
Figure 3B-7: Lateral view of the pelvis, showing the examining fingers just reaching the sacral promontory
Lateral to the midsacrum, the sacrospinous ligaments can be felt. If these ligaments are followed laterally, the ischial spines can be palpated.
Put two examining fingers, with the palm of the hand facing upwards, behind the symphysis pubis and then move them laterally to both sides:
Figure 3B-8: The brim of the pelvis
To measure the subpubic angle, the examining fingers are turned so that the palm of the hand faces upward, a third finger is held at the entrance of the vagina (introitus) and the angle under the pubis felt. The intertuberous diameter is measured with the knuckles of a closed fist placed between the ischial tuberosities.
Figure 3B-9: The pelvic outlet