Mary Cronk's thoughts on early detection of scar problems during VBAC

Mary Cronk MBE, has been a midwife since the early 60s and been practicing independently since 1990, has extensive experience of caring for VBAC and HBAC women. She discusses ways she feels she can enhance the safety of such women.

I have had quite a few women with CS scars on my caseload and while the risk of scar problems is low 1% or less in a spontaneous labour it does exist. This woman's uterus has been compromised. I do a few things in addition to standard care for VBAC women.

  1. At around 20+ weeks I am not surprised if the woman complains of stabbing or burning sorts of sharp lower abdominal pains. This is not uncommon and is I think due to breaking down of small adhesions and the consequent leakage of a few drips of serous fluid onto the peritoneum with the resultant pain. I ask the woman to remember the feeling of these pains and explain what I believe to be the cause. One has of course to be sure that one is not missing a urinary tract infection (UTI) or even an appendicitis and I would not hesitate to get a medical opinion if the pain/discomfort was more than very brief.
  2. I am not usually too bothered about routine ultrasound scanning as I am unconvinced that it improves outcomes. However as we know that one of the problems can be difficulty with the placenta if it has attached itself to the previous scar, I think a placental localisation scan around 35-36 weeks can be helpful and enable one to anticipate needing to transfer for help if the placenta is reluctant to separate.
  3. I take and record the woman's pulse rate during antenatal visits in the last month. This identifies the woman's normal pregnant pulse rate, and as I take the matenal pulse frequently in labour I have a prelabour datum. I have been surprised at just how fast pregnant women's pulses are, 84-96 being not uncommon, whereas in her non pregnant state it might have been 66-80
  4. During the last month or so of the pregnancy, I ask the woman to feel her abdomen and get to know how her scar feels. Are there any bits that are lumpy or a bit tender? In addition to having the woman know her scar, I have found that doing this can sometimes lead her to talking about her feelings about the previous CS and help us work through issues. I have cared for a woman who when I suggested that she felt her scar burst into tears and told me she had NEVER done so! We did a lot of work together and she had a lovely home waterbirth.
  5. In the labour, which is hopefully spontaneous at term (approx 37-42 weeks), I ask to be called sooner rather than later. In addition to the usual observations I take her pulse every 10 to 15 minutes to establish a baseline and I record it. Depending on what is happening I may or may not stay, but if I feel that labour is established I would stay. I make a nuisance of myself taking her pulse and I increase the frequency of this observation as the labour intensifies. It is not a totally reliable sign but should there be any dehiscence there is often a rapid increase in pulse rate and in my opinion it is worth doing. The mechanism is that any dehiscence or even overstretching of the scar can cause a leak of serum onto the peritoneum causing the surgical shock reaction resulting in an increase in pulse.
  6. I ask the woman to prod her scar as she knows best how it feels and tell me if anything gets different from usual. I also ask her to let me know if she has any pain between contractions particularly a pain that feels like the adhesion pains that she might have had at 20 weeks or so.

I believe all these signs and symptoms may identify a scar problem long, long before there would be any deterioration in the fetal heart rate. I know the received wisdom is that the CTG will pick up the fetal distress caused by a ruptured uterus and I know that acute rupture CAN happen but vigilant quiet careful observation of the mother can usually identify potential problems long before the baby is affected. These extra observations I am suggesting are of course in addition to the usual observations of fetal welfare and labour progress that one makes during any labour.

Mary Cronk June 2005

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