Descent of the fetal head
For labour to progress well, dilatation of the cervix should be accompanied by descent of the fetal head, which is plotted on the same section of the partograph, but using O as the symbol. But before you can do that, you must learn to estimate the progress of fetal descent by measuring the station of the fetal head, as shown in Figure 4.3. The station can only be determined by examination of the woman's vagina with your gloved fingers, and by reference to the position of the presenting part of the fetal skull relative to the ischial spines in the mother's pelvic brim.
As you can see from Figure 4.3, when the fetal head is at the same level as the ischial spines, this is called station 0. If the head is higher up the birth canal than the ischial spines, the station is given a negative number. At station –4 or –3 the fetal head is still 'floating' and not yet engaged; at station –2 or –1 it is descending closer to the ischial spines.
If the fetal head is lower down the birth canal than the ischial spines, the station is given a positive number. At station +1 and even more at station +2, you will be able to see the presenting part of baby's head bulging forward during labour contractions. At station +3 the baby's head is crowning, i.e. visible at the vaginal opening even between contractions. The cervix should be fully dilated at this point.
Now that you have learned about the different stations of fetal descent, there is a complication about recording these positions on the partograph. In the section of the partograph where cervical dilatation and descent of head are recorded, the scale to the left has the values from 0 to 10. By tradition, the values 0 to 5 are used to record the level of fetal descent. Table 4.1 shows you how to convert the station of the fetal head (as shown in Figure 4.3) to the corresponding mark you place on the partograph by writing O. (Remember, you mark fetal descent with Os and cervical dilatation with Xs, so the two are not confused.)
When the baby's head starts crowning (station +3), you may not have time to record the O mark on the partograph!
Table 4.1 Corresponding positions of the station of the fetal head (determined by vaginal examination) and the record of fetal descent on the partograph.
Station of fetal head (Figure 4.3)
|Corresponding mark on the partograph|
|–4 or –3||5|
|–2 or –1||4|
What does crowning mean and what does it tell you?
Crowning means that the presenting part of the baby's head remains visible between contractions; this indicates that the cervix is fully dilated.