4.6 Assessing moulding and caput formation
The five separate bones of the fetal skull are joined together by sutures, which are quite flexible during the birth, and there are also two larger soft areas called fontanels (Figure 4.4). Movement in the sutures and fontanels allows the skull bones to overlap each other to some extent as the head is forced down the birth canal by the contractions of the uterus. The extent of overlapping of fetal skull bones is called moulding, and it can produce a pointed or flattened shape to the baby’s head when it is born (Figure 4.5).
Some baby’s skulls have a swelling called a caput in the area that was pressed against the cervix during labour and delivery (Figure 4.6); this is common even in a labour that is progressing normally. Whenever you detect moulding or caput formation in the fetal skull as the baby is moving down the birth canal, you have to be more careful in evaluating the mother for possible disproportion between her pelvic opening and the size of the baby’s head. Make sure that the pelvic opening is large enough for the baby to pass through. A small pelvis is common in women who were malnourished as children, and is a frequent cause of prolonged and obstructed labour.
A swelling on one side of the newborn’s head is a danger sign and should be referred urgently; blood or other fluid may be building up in the baby’s skull.
4.6.1 Recording moulding on the partograph
To identify moulding, first palpate the suture lines on the fetal head (look back at Figure 1.4 in the first study session of this Module) and appreciate whether the following conditions apply. The skull bones that are most likely to overlap are the parietal bones, which are joined by the sagittal suture, and have the anterior and posterior fontanels to the front and back.
- Sutures apposed: This is when adjacent skull bones are touching each other, but are not overlapping. This is called degree 1 moulding (+1).
- Sutures overlapped but reducible: This is when you feel that one skull bone is overlapping another, but when you gently push the overlapped bone it goes back easily. This is called degree 2 moulding (+2).
- Sutures overlapped and not reducible: This is when you feel that one skull bone is overlapping another, but when you try to push the overlapped bone, it does not go back. This is called degree 3 moulding (+3). If you find +3 moulding with poor progress of labour, this may indicate that the labour is at increased risk of becoming obstructed.
You need to refer the mother urgently to a health facility if you identify signs of an obstructed labour. You will learn more about this in Study Session 9.
When you document the degree of moulding on the partograph, use a scale from 0 (no moulding) to +3, and write them in the row of boxes provided:
0 Bones are separated and the sutures can be felt easily.
+1 Bones are just touching each other.
+2 Bones are overlapping but can be separated easily with pressure by your finger.
+3 Bones are overlapping but cannot be separated easily with pressure by your finger.
In the partograph, there is no specific space to document caput formation. However, caput detection should be part of your assessment during each vaginal examination. Like moulding, you grade the degree of caput as 0, +1, +2 or +3. Because of its subjective nature, grading the caput as +1 or +3 simply indicates a ‘small’ and a ‘large’ caput respectively. You can document the degree of caput either on the back of the partograph, or on the mother’s health record (if you have it).
Imagine that you are assessing the degree of moulding of a fetal skull. What finding would make you refer the woman in labour most urgently, and why?
If you found +3 moulding and the labour was progressing poorly, it may mean there is uterine obstruction.