It is important to know and establish whether parturition has started. Frequently, the precise start of parturition cannot be stated. Three phenomena can be used to establish this.
- The presence of regular, powerful contraction activity. Contractions are uterine contractions that are painful and generally increase in intensity. The rule of thumb is: if, over a period of at least 1 hour, regular contractions occur every 4 to 8 minutes, which increase in strength and frequency, parturition has almost certainly started.
The subjective experience of contractions by the woman can strongly differ per individual. Irregular uterine contractions very frequently occur during the last trimester of pregnancy. These are so-called early contractions and they do not indicate the start of parturition. During examination, abdominal palpation can be used to objectively observe uterine contractions, when the hardening of the uterus can be felt. In this way, the duration and frequency of the contractions can easily be determined. The strength of a contraction can be determined by measuring intra-uterine pressure, although this is not usually necessary. The progression of dilation is usually the best evidence of effective contractions. It should be realised that examination of the uterus during a contraction is unpleasant for the woman. - The woman experiences a ‘show’. In obstetrics, a show means that the woman loses a plug of vaginal mucus mixed with blood. The mucus originates from the endocervical crypts. The blood loss is probably caused by the membranes detaching from the cervix and/or tears arising in the cervix during dilation.
- The membranes rupture. This is popularly known as the water breaking. Since the membranes are flexible and mobile structures, it would be more appropriate to speak of the membranes ‘tearing’. In a physiological pregnancy, the membranes usually rupture at the end of the dilation phase. Sometimes, the rupturing of the membranes occurs before dilation contractions develop, and amniotic fluid leaks out. The quantity can vary considerably. The woman may perceive this sensation as involuntary urine loss. If doubts arise, amniotic fluid can be recognised by its sweet smell and from the vernix flakes that full-term amniotic fluid contains.
Membranes can also rupture without any contractions taking place. This early rupturing of the membranes increases the risk of an intra-uterine infection occurring. That is why in the absence of good contraction activity, vaginal examination is contraindicated in the case of ruptured membranes, unless this is necessary for other reasons (e.g. foetal distress and/or suspicion of a prolapsed umbilical cord).
When has parturition started?
Depending on the contraction activity, the condition of the membranes and whether or not there has been a show, an estimate will have to be made as to whether parturition has started. After that, a vaginal examination will be performed. The moment at which the woman is told that parturition has started will have to be chosen carefully. If she thinks that she has started labour too long before the expected delivery of the child, it is referred to as a ‘false start’ and, as a result of disquiet, pain and anxiety, she may become exhausted before the actual dilation stage has started.
If a woman is experiencing regular painful contractions that occur every 3 to 5 minutes and last 40 to 60 seconds and there is considerable dilation or progression in the dilation during consecutive vaginal examinations, it can be assumed that under normal circumstances that the child will be born within 24 hours.