Opinions differ regarding the value of routine internal pelvic examination for assessment of the small, bony pelvis as a birth canal. One disadvantage of not performing an internal pelvic examination, or postponing the internal pelvic examination until late in the pregnancy can be that the head or the buttocks is too deeply descended into the pelvis for a reliable examination to take place. Under special circumstances, if the child is lying in the breech position in a nulliparous woman, previously-performed reliable pelvic examination is crucial for determining future management.
Procedure
- Insert the examining fingers behind the symphysis [Figure 5].
Figure 5
- Feel for irregularities, such as a ridge on the symphysis.
- Feel the linea terminalis by allowing both fingers to follow the edge of the pelvic brim from the symphysis to the sacral promontory [Figure 6]. Normally, the linea terminalis cannot be followed for more than 2/3 its length.
Figure 6
- Determine the diagonal conjugate. This is the distance from the lower edge of the symphysis to the sacral promontory.
- Place the radial side of the index finger against the lower edge of the symphysis.
- Localise the sacral promontory with the tip of the middle finger. Normally, the promontory will be out of reach [Figure 7].
Figure 7
- However, if the sacral promontory can be reached, place the index finger of the other hand as close as possible against the symphysis and place this finger against the internal finger [Figure 8].
Figure 8
- Remember this marking point. Once the examination has been completed, measure the distance from the marking point to the top of the middle finger using a tape measure. To calculate the true conjugate, subtract 1.5 cm from this distance measured (diagonal conjugate).
- Feel along the sacrum from the promontory to the coccyx [Figure 9]:
- The sacrum should be biconcave (curved in both the transverse and longitudinal planes).
- The sacrum should contain no ridges.
- The coccyx should not be pointing inwards.
Figure 9
- Determine if the ischial spines protrude more inwardly than normal [Figure 10].
Figure 10
- Determine the width of the pubic arch. Do this by placing the index and middle finger of the right hand next to each other in the angle of the arch [Figure 11]. The width is normal if the angle is 90°. In principle, this may be assumed if two fingers can be placed next to each other in the pubic arch angle.
Figure 11
- Remove the fingers from the vagina.
- Make a fist.
- Measure the distance between the ischial tuberosities [Figure 12]. Normally, four knuckles of a male hand (about 9 to 10 cm) will fit tightly between the ischial tuberosities. A female hand is about 2 cm smaller.
Figure 12